Adapted from a recent online discussion.

Hi Carolyn: I am three months post-breakup with my BF of over a year. He cheated on me and left me for someone else. This after he said he knew how much it hurt to be cheated on (his ex-wife cheated on him) and wouldn't do it to someone else. When he found out his ex-wife was getting remarried, he flipped out and got together with some woman at work (before breaking up with me!).

I would have thought his heinous and selfish behavior would help me be glad I was free of him -- indeed, my friends are glad. Instead, I am obsessed with images of him being happily coupled with the office hooch he left me for, while I am in the proverbial fetal position mourning his betrayal. Any thoughts that might help me regain perspective? -- Breakup Blues

I can see the temptation to blast yourself with "He's scum and he didn't deserve me!" propaganda, and I can see why your friends are trying it for you. It's usually our first resort when we hope to salvage some pride and self-worth from a catastrophic humiliation.

But I'm not sure it applies here, which may be why it's not working.

Is what he did, technically, a betrayal? Of course. It also exposed the emptiness of his promise, and made you feel like a fool for believing him, and all the other fun stuff that comes with getting dumped.

I just don't think his was the significant lie exposed here. The real whopper is that the world is black-and-white enough for an "I'll never cheat on you" promise to mean anything. As a shield against pain, those words are absolutely, flat-out meaningless.

I actually believe (from what little you wrote here) that even he probably believed his promise. But he also had no idea what he'd do if someone dropped his emotional foundation in a box and shook it really hard.

So, what you're processing right now isn't just that someone you counted on can hurt you in the one way you thought he wouldn't. You're processing the full force of the saying "Anything can happen."

Anything can happen. A faith in other people can't be what gets you out of bed in the morning, or else you're in for a terrible letdown.

A faith in yourself, on the other hand, that you can handle whatever happens, is something that really can sustain you.

In fact, confidence in your ability to weather betrayal is the foundation of trust: Without it, you're suspicious of everyone.

This isn't as cynical as it sounds; we do build relationships, through which we build trust, and we reinforce that trust through commitment. Not with words, but with actions and time. Most people do mean well, and believe they do right by other people.

But even then, it doesn't always work out perfectly, which brings you back to the thing you have to be able to count on: You.

So use this smack in the face to develop some of this kind of resourcefulness. Stand up, brush yourself off, wish this guy -- who clearly has emotional damage of his own -- some genuine happiness, and start concentrating on the things that will help you carry on.