Why is it that when you’re finally over someone, he comes back to make your life miserable anew and disrupt your peaceful existence?

All this time I thought that I was finally over Jim. But was I ever wrong? Once I’m done with guys, I’m done with them. There’s always an exception and he is definitely the one exception. I don’t know if this is love, obsession or whatever. I certainly missed Jim but I don’t want history to repeat itself, with me on the losing end. I am thinking of getting even with him for the humiliation he caused me the last time, but doubting myself to pull that off. I’m also thinking of taking these things seriously for a change but I can’t afford being hurt in the end. Paranoid? Maybe. I really don’t know. I’m in a terrible shit right now.