A guy I dated on a serious long-term basis 10 years ago just told me he cheated on me.?

Even though you moved on, and probably felt closure after the relationship, and got on with your life, it may hurt now because you actually had closure. But finding this out now, can hurt even if you moved on because you had closure, and because the relationship was important to you. You might think that he didn't think the relationship was as important to him as it as to you, which may be true. (No offense, happens to everyone). Or you may feel betrayed too because he as someone that you trusted, and someone that you never thought would do that to you, and now finding this out, you think that well I trusted this guy, and we were serious, so my current, or future boyfriend, if you don't have one, could do this to you. My advice, move on. I know it may hurt now, and it may be hard to trust people knowing this, but not all guys are cheaters. And if he cheated on you, he isn't worth your tears. As for him telling you now, I honestly have noooo idea. He may realize that he messed up and wants you back, he may feel guilty, or depending on how you broke up, he may be trying to get back at you. I'm not really sure. But I hope my advice helps you and I hope you realize that he's not worth it, and that not all guys are like that.