That guy you had a thing with a while back? Still under your skin. Some splits aren’t divorce-level traumatic, yet they can wreak long-term havoc. Here’s how to say good-bye (and feel better) for good.

By Valerie Frankel
Updated January 20, 2015
Anna Parini

Remember the days when you could dump/be dumped and never see your ex’s stinking face again? Now, thanks to Facebook, Twitter, Instagram, and the like, his (annoyingly still handsome) mug is on display daily. And it’s all too easy to start obsessing over any digital detail, like a time stamp (“He was out until 2 a.m.!”) or a location (“She’s at a café a block away!”). Even relatively small splits—say, a break with a six-month boyfriend—can take a lot of time to get over, particularly now that these exes seem to (digitally) follow you wherever you go. So what can you do about it?

When it comes to romance, “it’s not the intensity or the length of the relationship that dictates how you feel after it ends,” says Jane Greer, Ph.D., the author of How Could You Do This to Me? Learning to Trust After Betrayal, ($13, “The trouble is caused by the unresolved emotions that the breakup triggered. You’re left with loss and a desire to understand what happened.” Then you have to detox—flushing that person out of your system. For a 2005 study published in The Journal of Comparative Neurology, subjects were put into brain-imaging machines and shown photos of their romantic partners. The areas of the brain that lit up included parts of the reward system, similar to the ones that light up when an addict gets a fix. “A breakup is a withdrawal. It reinforces the separate self, the ‘you’ from ‘we,’ and is essential to healing,” says Greer. Even if you were the one to pull the plug, you still yearn for what you know. “You have to learn how to adjust to being without,” says Greer.

After weeks of detoxing, communication with an ex feels like a relapse. Sending an e-mail or a text, even a nonchalant “Just wanted to say hi,” is akin to disclosing, “I can’t quit you.” “Contact sustains longing and keeps the addiction alive,” says Greer. “Going cold turkey is hard, but it’s the fastest way to move on.”

But why do the memories of an old flame or a torturous one-night stand still rankle after a lot time has passed? “If the experience was packed with rejection, it’s difficult to come to terms with,” says Greer. “Bad feelings can take on a life of their own and persist.” That’s why, years later, while enjoying brunch with your husband, when you read the wedding announcement of your long-ago fling, you might want to throw up. Just a little. In your mouth.