Q: My boyfriend broke up with me almost five years ago, but I still can’t get over what he did to me. We had an open relationship, but he still lied to me about how many other guys he was fucking, and broke all the agreements we made. He lied to me about everything. He borrowed money from me and never paid me back. He was completely self-centered. We only did the things he liked to do, and whenever he didn’t get his own way he’d throw a tantrum. One day he just moved out while I was at work, without even saying good-bye, leaving me having to pay the rent by myself. Every day I go over and over in my mind the things he did, all the things I should have said, and how I could have acted differently. Since he left I’ve had occasional hook-ups, but I haven’t been able to meet anyone that I might get into a relationship with. I want to move on, but every day I think about him until I work myself up into a rage and get completely exhausted. I know I’d be better off if I could just forgive him and go on with my life, but I can’t let him off the hook. What can I do?

Holding this kind of resentment is like mixing a cup of poison for someone else and then drinking it yourself. Grudges are like addictions. They keep us fascinated the way a moth is fascinated by a flame, and to the same self-destructive effect. Your boyfriend stopped hurting you long ago. He’s no longer the problem. It’s your own mind that now torments you every day, and so it’s your mind that is the issue now. In a sense, you’re in a trance state whenever you’re preoccupied with your resentment. The question is how to wake up. This is exactly the sort of question that good psychotherapy can help answer.

In my experience, these kind of obsessive ruminations serve a defensive purpose. They mask awareness of inner feelings or ideas you don’t want to notice by keeping your attention focused outwardly on the injustice the other person committed. They’re like hard shells protecting your soft heart. The way to stop feeling at the mercy of your resentment is to go beneath it to the vulnerability you’re trying to ward off through anger.

Only your self-inquiry, guided by a competent therapist, can reveal what is behind your resentment, but if I were to hazard a guess, I would consider the possibility that it’s purpose is to ward off unacknowledged feelings of guilt. I suspect this for several reasons. First, it sounds as if this guy walked all over you while you were together, and when people allow this to happen to themselves, unconscious guilt over asserting themselves is often the reason. Second, when we “protest too much,” we’re often doing it because we don’t really completely believe what we’re saying. Third, there is obviously something self-punitive in the mental torment you’re going though. Finally, you’ve apparently been holding yourself back from getting into another relationship all these years. Could it be that you’re not allowing yourself another chance at love because you feel guilty about what happened the last time? Since all of this may sound like blaming the victim, I should emphasize that you don’t have to be actually guilty of anything in order to feel deeply at fault. Irrational guilt is one of the most common sources of emotional suffering, and unreasonable self blame is far more destructive than realistic remorse.

You might actually believe, on the deepest level, that your boyfriend was right to leave you, either because you imagine you failed him in some way or because you were somehow unworthy of his love. If you feel something like that, then, by constantly pleading your own case in your obsessive ruminations about the wrongs he did to you, you deny your own feelings of guilt while simultaneously atoning for them for them by making yourself miserable. These guesses of mine may be completely off the mark: I offer them only as one example of the kind of unconscious processes that might be keeping you stuck.

On the question of forgiving him and “letting him off the hook,” I don’t think he’s on any hook at all. It’s’ you who are impaled on your memories. And anyway, he’s hardly at your door, hat in hand, asking for forgiveness. The real issue isn’t forgiving, it’s letting go. If unconscious guilt is really your issue, and if you can face it and work through it, you’ll may finally find yourself able to believe wholeheartedly the things you’ve been telling yourself about his character. And if you can do that, you’ll be in a better position to stop obsessing about him because you’ll really know that he isn’t worth it and that you deserve better.

Tom Moon is a psychotherapist in San Francisco. His website is tommoon.net.