How to get over an ex?

Ok, I've always been a loner, and I finally let my defenses down and gave someone a chance. We were together for two years - he was so doting and sweet, I thought he was the one. Now we are over. I cannot help but dwell on the special memories we had, and feel so sad.... He was my first and only relationship and now it is over. I didn't want to deal with it, but now he has a new girlfriend that he is crazy about. I am still missing him, and am so angry at myself for not being able to put this behind me. I also hate how cliche/pathetic I sound. I guess I just need some advice as to how (if possible) to move on. I know I sound a bit on the pathetic side, but wow, I had no idea how much breaking up would hurt. Wish I never would have let him into my life.... :(