Last year, I broke up with the man I was engaged to and loved deeply. I'd found out he was cheating on me constantly with many different women throughout our relationship. My life has gone on, but I often think of what he did to me and feel incredible anger. I'd like to forgive him, but I'm not sure how to do that when these feelings pop up throughout my week.

It's hard to move on emotionally when you not only have a grudge but take it everywhere with you like a cockroach on a little yarn leash.

This isn't to say you should forgive the guy. There's this assumption that forgiving someone who's wronged you is the healthy, constructive thing to do -- and, sure, it can be. Evolutionary social psychologist Michael McCullough defines forgiveness as "an internal process of getting over your ill will for an offender." He explains that forgiveness is "adaptive" -- functional, beneficial -- when there's a valuable relationship at stake: when you'd benefit from continuing contact with the perp (and it seems unlikely they'll be a repeat offender -- harm you again in a similar way).

But you aren't looking to re-up with the guy! And you probably have zero indication he's changed anything -- aside from which woman he's two-timing (or, uh, 22-timing, as a rough quarterly estimate). What you're really seeking is peace of mind. Consider that anger, like forgiveness, can be functional. The anger you still have probably remains for a reason: a warning sign that you're in danger of being cheated on again. But there's a way to shut off that alert -- and protect yourself in the future -- and it's by turning this into a learning experience.

Be accountable for the part you played in what happened -- not because, "Yay, blame the victim!" -- but because it's the part you can control. Did you, perhaps, want so badly to believe you'd found love that you ignored signs you'd landed a cheating creep posing as an adoring boyfriend? Being honest about what you could -- and should -- have done differently can become your guide for what you will do differently the next guy around. A man can give you the sense he has a moral compass, but it's best you give it a hard look to see it isn't cracked and dusty from constantly being dropped in other women's bedrooms.

For pages and pages of "science-help" from me, buy my latest book, "Unf*ckology: A Field Guide to Living with Guts and Confidence." It lays out the PROCESS of transforming to live w/confidence.