Four months ago, I started hooking up with this hot guy I met on Tinder. He isn't someone I'd normally go for; he's a total mess and serious trouble. He always made me come to his place, and I always left feeling gross rather than satisfied. However, about once a month, I'd feel attached and confess this to him. He'd go into hiding, but he always came back for sex. The whole thing made me worried, anxious, and sad, so I deleted his contact info, but I miss him and think about him constantly. How do I stay strong? If he texted me, I'd just run back to his bed.

--Detoxing

Sex that turns your stomach is a small price to pay for romance, like a man whispering sweet nothings in your ear: "Just leave your coat on. This won't take long."

Yes, it's pretty amazing to find yourself missing a man you dislike and maybe even despise. This probably comes out of how there's a potentially higher price for women from naked fun -- ending up with a sex dumpling (uh, child) -- and whoops, where did that Hunky McHunkington run off to, now that the kid needs food, diapers, and a college education?

Because women can get "impregnated and abandoned," anthropologist John Marshall Townsend explains, female emotions evolved to act as an "alarm system" to monitor the "quality and reliability" of male investment and "remedy deficiencies even when (women) try to be indifferent to investment." In a study of Townsend's I've referenced before, even when women wanted nothing but a shag from some dude -- basically seeing him as useful meat -- they often found themselves fretting the morning after about whether he cared about them or only wanted sex.

These women aren't mushy-minded idiots. Chances are, they've been roofied into these feelings -- by their own bodies. Oxytocin -- a hormone associated with emotional bonding -- gets released in both men and women through cuddling, kissing, and orgasm. However, men's far greater supply of testosterone -- especially when they aren't in a committed relationship -- can act as a sort of nightclub bouncer, blocking the uptake of oxytocin.

As for the monthly pull this guy has on you, research by evolutionary psychologists Kelly Gildersleeve and Martie Haselton suggests that once a month -- during ovulation -- a woman seeking casual sex is more likely to be drawn to a cad's more masculine features (like a square jaw and a muscular build). As for how you might quit this particular cad, let's get real. Deleting somebody's number doesn't stop them from calling. You've got to block his number. You might also use free smartphone apps -- like Productive, to motivate yourself by ticking off the days you've gone cadless, and Clue, to track your ovulation. For added fortitude, make a list of the ways sex with him makes you feel. Being worried, anxious, sad, and grossed out can sometimes be a reason to get a man over pronto -- but only if he's a miracle worker of a plumber.