I met this man a few years ago, and it was like a thunderbolt struck us -- the stuff movies are made of. He told me that his female roommate was just a friend. We went on a few dates before I realized she was actually his girlfriend. He promised that they were going to break up, so I hung around for a bit, but of course it never happened. Last year, I ran into him, and he said he was no longer with that woman and wanted to date me. I turned him down flat because I figured that if he was going to lie and cheat on her, then he would do the same to me. I'm kicking myself now because I have never met anyone like him. Is it really "once a cheater, always a cheater," or could it be different for us? I have to put this to bed in my mind because I can't stop thinking I missed out on "the one."

--Opportunity Lost

Sure, your encounter with this man was "the stuff movies are made of" -- the ones in which Godzilla comes clomping through town and puts his big clawed foot through the roof of some poor villager's house.

What you should be doing is tiring your arm out by patting yourself on the back. You showed presence of mind in drop-kicking "the one" -- the one who, before long, would have been in a bar telling some woman that you're just his "roommate." But now your loneliness is telling your logic to put a sock in it, luring you into a common error in evaluating risk that behavioral economists call "optimism bias." This is best explained as the "I'm special!" bias and involves the unrealistic thinking that the bad things that befall other people will see us and go, "Nuh-uh...no way...not her!"

Though we know -- usually from painful experience -- that character change is hard (and rare), optimism bias leads us to flirt with bright ideas like "Maybe he's done with the cheating!" It's probably easier to think that now, not having seen him for a while. And the reality is, even serial killers sometimes go dormant. This shouldn't be taken as a sign that they've grown weary of cutting up the neighbors and storing them in Ziploc bags in their freezer.

Real change, when it happens, comes with signs there's been a transformation -- like expressions of deep remorse about being unethical and a sea change in a person's moral standards. And these are just the preliminaries. Character change is revealed through action -- over time. Sure, you could keep this guy at arm's length for a year while you observe his behavior. Or, instead of hoping against hope for character change, you could opt for a change of characters, as in getting out there and meeting new men. Should you fall back into feeling wistful about this guy, remind yourself of German psychoanalyst and philosopher Erich Fromm's thinking that love isn't just "a feeling"; it's something you do (in this guy's case, to more than one woman at a time). Or as one of my other favorite 20th-century philosophers, a Dr. E. Fudd, put it, "Good widdance to bad wubbish."

I often come off needy and desperate, so I'm trying to play it cool with this great new guy I'm dating -- a new and difficult tactic for me. There are two other guys who are into me. I'm not into them, but I'm tempted to keep them on the back burner -- you know, throw them a few crumbs now and then to keep them hooked so they can be a distraction from the new guy. I know this is user-y, so I haven't decided to do it, but I also haven't come clean about where I'm really at. And I have to admit I don't mind the validation they give me. Ugh.

--Torn

If you're going to turn men into emotional support knickknacks, why not go all the way? Cut their hearts out and stick them in Mason jars with cute labels written in glitter pen.

What you're contemplating is romantic fraud. Sure, stacking up irrelevant men like firewood so you can climb into the arms of the man you want is easier than exploring why you "often come off needy and desperate." A wild guess: Because you are?

Typically, this comes out of trying to use a guy for jobs he can never fill, like making you feel okay about you. If that's the problem, get to work on fixing it. In the meantime, avoid coming off needy and desperate by acting like a woman who might end up wanting a man but doesn't need him. That woman doesn't barrage him with calls, texts, and surprise visits -- or text back with an immediacy that suggests she's been hovering over her phone like a starving hawk circling the den of the last prairie dog on earth. Get your restraint where you can, like by responding to a text from him by giving your phone to somebody to lock in a drawer for an hour. Waiting to text back will help you come off like the woman you should try to be, one who embodies the understanding that emotional security comes from within -- and no, not from within a bunch of other people.

There's a girl who works at the hotel where my co-workers and I go for drinks. She's hot and smart and fun, and I really like her and want to ask her out. The problem is that when she laughs, she cackles in this really annoying way. I'm wondering whether, if we started dating and hit it off, I could subtly hint to her that she should change her weird, witchy laugh. Because, honestly, she's perfect otherwise.

--Bothered

It's great to find a woman who laughs at your wit, but not when she sounds like she'll follow up with "I'll get you, my pretty, and your little dog, too!"

I know, the "expected" reply to a man wanting a woman to change something about herself is, "How dare you, you shallow pig?!" And I'm aware that behaviors that initially seem mildly annoying can, in time, make you want to bludgeon the person with the soup ladle. But it does seem a shame to nix a woman you really like right off the bat simply because it's hard to tell whether she's laughing or you're around the corner from a donkey engaged in erotic asphyxiation.

It's possible that her laugh really is her laugh, "designed" by the shape and location of her larynx. HowStuffWorks founder Marshall Brain explains that when we're laughing, the larynx gets half-closed by the epiglottis. (Laughter, most charmingly, is the sound of a person struggling for air, which we each do in our own special way.) But the reality is, some people with disturbing laughs have created them, often out of a desire to seem unique or get attention. They repeat their fabricated ha-ha, and it becomes part of them. And then time passes, and they forget to check whether their creation is still serving them or whether it might be to potential dates what garlic and crosses are to working vampires.

Obviously, a woman is likely to be hurt and offended if you announce, "If we're going to have any future together, you'll need a laughectomy." However, IF you started dating her and IF you saw that she's one of those (rare) people who "would rather know," you could ask her about her laugh: "Have you always laughed that way?" But brace yourself for her to come back with something like "Do you hate my laugh?" At this point, like a rat on flotsam after a shipwreck, all you can do is grab for a piece of flattery: "Uh, um...it's just that you're so elegant. It doesn't seem to go with the rest of you."

But first things first. You haven't even asked her out. She might say no (laughing raucously and scaring away crows). Or, if she said yes, things might fizzle after a date or two. So maybe go out with her a few times, taking it slowly (no sex, tickling, or comedy club visits), and weigh whether her general fabulousness is enough to offset the intermittent cackly audio. Who knows...maybe you'll fall for her to the point where her laugh becomes endearingly awful -- always making you long to grab her and kiss her in the back seat of her broomstick.

The guy I'm seeing revealed that he is hesitant to get into a relationship because it means "taking responsibility" for another person on a level you don't have to when you're just friends with benefits. In his words: "I mean, what if you got cancer?" He wants the friendship and connection of a relationship, but he inevitably fails to step up and women bail. (What a surprise.) He did have a three-year relationship in the past, and I really like him. Should I stick around and hope he calms down?

--Unsure

Here's a guy who will have your back -- getting smaller and smaller in his rearview mirror at the first sign of a serious problem, such as a bad hangnail. Sadly, it isn't enough to "really like" a guy. You need to really like a guy who's prepared to respond to your needs with loving concern instead of burning rubber. And in keeping with this unfortunate automotive theme, assessing a guy's boyfriendability should be approached like selling cars. The successful car salesman will not spend his morning singing the praises of heated seats and in-car Wi-Fi to the customer wearing a blanket and cardboard sandals. That guy sure could use a car, just as your guy sure could use the "friendship and connection" (and, no doubt, the sex) of a relationship, but neither will be able to make the required payments. So, yes, waiting and hoping this guy "calms down" is an option -- but you'd probably have better luck waiting for the brown bird outside your window to turn into a UPS driver.

I recently started dating this new girl. I asked her whether her lips and boobs are real (and it turns out they are). However, I did call her out on having a nose job. She admitted it but seemed kind of upset. It's the truth. And she's beautiful, however she got that way. What's the problem?

--Just Curious

At least you didn't hold her up to the light like a hundred-dollar bill to look for the hologram.

The fact that you have a thought is not reason enough to let it out to roam the streets, exposing itself to the ladies. As I write in "Good Manners for Nice People Who Sometimes Say F*ck," at the root of manners is empathy. So before speaking to someone -- especially someone you're dating -- ask yourself, "Gee, wonder whether she'll feel all warm and fuzzy inside when I point to her boobs and ask, 'Yours or cubic zirconia?'"

The reality is, people often spin the truth to present themselves in a better light, just as businesses do. (Your cable company does not really "value your time," and unless you're a wino, I'm pretty sure Miller High Life is not "the Champagne of beers.") However, evolutionary psychology research by William Tooke and Lori Camire finds that men and women tend to fudge their presentation in different ways. Because women evolved to prioritize men with the ability to "provide," men are far more likely than women to be deceptive about their finances. (You sure don't see women doing as a male friend of mine did. He lived in a dumpy apartment and drove an old Nissan that looked like it got used for soccer practice by Godzilla and Mothra, but he had me take a photo of him for his online dating profile in a beautiful neighborhood -- in front of some stranger's Porsche.)

On the flip side, because men evolved to prioritize physical attractiveness in women (with the features men find beautiful reflecting health and fertility), women are most likely to be deceptive about their looks (those factory installed by the assembly line boss known as Mother Nature). That's why women are extremely sensitive about a man parsing their appearance -- as men are when a woman sizes up their finances and position. So, for the future, keep in mind that there's a reason the term is "beauty secrets" and not "beauty announcements." To reset the balance -- so she isn't insecure about your feelings regarding her appearance -- get in the habit of saying something nice about what she's wearing and if she looks particularly sparkly some night. And do try to maintain perspective on the level of transformation here. She was merely born with a different nose; she wasn't born "Alan" or "Bruce."

I'm a reformed party girl. I used to go out, get drunk, and sleep with lots of guys on the first date (if you could even call some of these "dates"). I am older now and am ready for something serious. But after hearing me talking about how I used to be, guys campaign for first-date sex. We'll start making out a little, and I get into it and end up doing stuff before I really want to.

--Regrets

No guy wants to hear, "I really like you, so I'll make you spend months jumping through hoops while catching a little ball in your teeth instead of having sex with you right away like I did with those 6,000 other guys." In fact, "I don't do that...anymore" is pretty much a challenge to a guy to try for the same deal the other guys got. So consider talking about the person you are instead of the person you were. In fact, you might avoid going into any real detail -- ever -- about the old you. As psychologist and linguist Steven Pinker points out in "The Stuff of Thought," the ability for a person to deny or overlook what he hasn't exactly been told is a powerful force. (No guy wants to think about all the ghosts of penis past.)

You can also preplan to make it hard for yourself to cheat, a technique called "precommitment," recommended by economist Thomas Schelling. For example, because alcohol and moonlight tend to combine to form a waterslide into your bed, you could schedule your first few dates at a less sex-friendly time and place, such as 10 a.m. at the coffee bar. Then if you go for a post-date walk, at least it won't be "the walk of shame." Before long, you should find that you have a new habit -- ending dates with "looking forward to seeing you again" instead of looking for your panties under a guy's bed.

I just moved in with the love of my life. Her former boyfriend from years ago lives in her downstairs "granny unit." My girlfriend recently revealed that along with financially subsidizing him, she's still doing his laundry because "it's just easier." He is 50 and previously earned a lot of money repairing computers and being a handyman, but he is not "into" working. My girlfriend is a therapist and sees a therapist, who has advised a proper separation. Amazingly, my girlfriend would rather she and I move out than insist he leave (though the home and loan are hers!). I'm worried that this will be one long, frustrating ride.

--Dumbfounded

Kids these days grow up so fast. Before you know it, they're 50 and back home doing bong hits in the basement.

Though you see your girlfriend as the preyed-upon one here, consider that she's getting something out of this, too, like feeling needed and conflict avoidance. Being conflict-avoidant means refusing to experience legitimate adult discomfort -- like the ouchiepoo of telling a full-grown able-bodied man that he needs to go get a job, an apartment, and a roll of quarters to do his own damn laundry.

We evolved to be a social species and to care about how others see us. However, we can take this too far, as your girlfriend has, probably out of an overvaluing of relationships (over self) and an ensuing desperate need to be liked. This leads her to shove away her needs, making her the perfect mark for an aging and manipulative slacker -- to the point where she stops just short of cradling her adult baby in her lap and feeding him a bottle of pale ale.

Life involves making trade-offs. On the one hand, you call her the love of your life. On the other hand, she comes with a man-sized tumor that she seems unwilling to excise from her life and yours. Whatever you decide, avoid telling her what to do (which generally provokes defensiveness, not change). Instead, you can tell her where your "nuh-uh, can't do" point is -- like if you ultimately can't live with a woman who is in a relationship with you but has one foot (and her wallet and a couple of laundry baskets) squarely in the life of her ex.

It's possible that a real likelihood of losing you could do for her what having a therapist and being a therapist could not -- compel her to act assertively. However, you do take a risk in drawing the line. You may decide to just suck it up to keep her, even if it means keeping him. If so, try to focus on the positives of having an adult toddler around -- like how he should only need to be taken to the emergency room for the occasional cardiac event and not because he's put yet another bean or Lego up his nose.

I started dating a female co-worker. I've seen many office romances go bad and be fodder for gossip, so I act very professional at work so nobody knows. She's hurt that I'm keeping her a "secret."

--Stressed

It's a bit of a disconnect to get the office hello from a guy who, just the night before, was undressing you with his teeth.

But the real problem here isn't conflicting ideas on whether to put out an all-office memo: "The softball team will meet at 5:30 p.m. behind the building, and oh, yeah, Amber and I are doing it." Differences of opinion are part of every relationship. What helps your partner feel okay about them -- even when she goes along with what you want -- is acting like you're in a relationship, not a dictatorship. This means figuring out policy together instead of your single-handedly deciding it and then -- surprise! -- greeting her like you aren't quite sure whether she's Amber who just helped you break your headboard or what's-her-face from sales.

Had you made this a discussion instead of a decree, she might've told you she's worried you're ashamed of her -- allowing you to reassure her (assuming you're not). Well, there's no time like now to have that policy discussion -- including worst-case scenarios, like how you two would handle it if things went south. It does seem prudent to wait to alert your co-workers until you're reasonably sure your relationship has legs. However, sooner or later, somebody from the office is likely to run into the two of you out on the town. The story of a Saturday night strategy session in the parking lot of a romantic French restaurant is unlikely to fly -- especially when it appears to have ended with both of you wearing her lipstick.

I'm a woman in my early 20s. I do fine getting dates, but only first dates. And no, I'm not having sex with guys on the first date, but I still never hear from them again. I ran into one of these guys at a party and begged him to tell me what had gone wrong. He said, "You're kind of intense." I asked him to explain, and he said, "You do a lot of talking." I do talk a lot, but I'm informed and opinionated. Do I really have to be some mute little woman to get second dates?

--Man Repellant

On a date, you should merely be splashing your personality around, tempted as you may be to hold a guy down and try to drown him in it.

This isn't to say you have to be "some mute little woman" to get a second date. Consider that there's a middle ground between channeling Nancy Grace and playing a shy geisha hiding behind her fan. And sorry, but being "informed" and "opinionated" does not give you a pass to turn a date into a re-education camp with wine and entrees. In fact, this sort of conversational takeover is like a toupee; it usually ends up calling attention to whatever it was supposed to cover up (self-worth issues, nervousness, or maybe a need to push people away, despite putting yourself out there like you want a relationship).

To see more of these guys than their exhaust as they drive away forever, be mindful of the purpose of a date: getting to know somebody, not getting to know how they look listening to you. As for all this information you're excited to impart, ironically, the way you get somebody interested in listening to you is by showing interest in them. You do that by listening to them -- really listening (from the gut, not just nodding while waiting for them to take a breath so you can shoehorn in your next point).

Being willing to share the conversational space isn't a sign you're some empty dress of a woman; quite the contrary. It's what secure people do -- connecting with others instead of pepper-spraying them with words. Try an experiment on your next few dates. Say as little as possible about yourself all evening. Answer questions about yourself when asked, but focus on asking your date about who he is and what he thinks. Chances are, you'll have a much better time and maybe get asked on some second and third dates. Wonderful things can happen when you give a man the sense that there's a real reason for him to be there -- as opposed to the idea that he could have stayed home and, in his place, sent a giant ear.

Four or five months ago, I had an amazing dinner date with this guy. I ended up sleeping with him afterward, and he disappeared. Out of the blue, he contacted me, wanting to take me to dinner. How do I know he won't pull the same jerko Houdini move?

--Suspicious

When you're on a first date and you'd like there to be a second date, it's okay to leave a little lipstick on the rim of the glass. Your face should not end up smeared across the guy's pillow.

Sure, there are couples who had sex on (or even before) the first date and have spent the next 67.3 years living happily ever after. But if you're a woman wanting a relationship, be mindful that sex on the first date is a risky strategy. As researcher Anne Campbell dryly put it, "Women's mate value is perceived to be low if they are willing to agree to low-cost sex" (as in, casual sex). A man will probably take it if he can get it -- but he's likely to, as they say, "sex it and exit."

As for this guy, he's already shown you that he IS someone who pulls "jerko Houdini" moves, with not so much as a texted "thx 4 putting out!!" the last time. If despite that, you agree to see him again, what prevents him from disappearing after sex is your ending the evening with your clothes on instead of on his bedroom rug. Unfortunately, the heat of the moment tends not to be home to Spock-like rationality and reserve. To guide how soon you'll get naked, go into a date with your ultimate goal in mind -- whether you have what anthropologists call a "long-term mating strategy" or whether you aren't so much looking for Mr. Right as you are Mr. Right Next To You At The Bar.