Thanks to a very insightful person on this forum, I've realized what exactly went wrong in my relationship. I think me and my ex were probably equally at fault. Our personalities were simply just too different. But I wrote the ex a letter explaining some things we never had the chance to talk about the night of our break up. Since I caught him at a bad time, and he didn't want to talk, I never had that closure that comes with most break up discussions. I told him there was no need to reply, but that I'd come to realize some things I wanted to put out there - if he wished to read them.
I don't really want to get back together with him, and I don't for a second think he would want to get back together with me. I'm sure he's already moved on by now. I just wanted to make it clear, in a very kind way, what I needed that I wasn't getting, and that I realized I had begun to drive him crazy - precisely because I was going crazy not getting what I needed. I guess I was worried about his conception of me after the break up. I didn't want him to think I was a crazy bitch of an ex. I felt the need to try to smooth things over and let him know I wished all the best for him.
As I don't expect to hear from him, I feel like I have some kind of closure now. At least, if he even bothers to read my email, then he'll understand things from my point of view, and that I still care about him as a person. Had he done anything horrible to me, I wouldn't have cared what he thought... but he was a good guy, and it was just unfortunate our respective flaws got in the way of our relationship.