How come I can't move on from my break up?

I met a girl and we were together for about 8 months. She meant the world to me, I gave up a lot to be with her (moved, changed jobs). Yes, I know now that this was a mistake, but I can't go back. She broke up with me, and 3 days later was with someone else. I've tried to reconcile, but there is no hope. The last time she spoke to me, she told me to move on. But my days are gray, and my nights worse. I'm in a new town with no friends, no family and it sucks. It's been about two months. Any advice? Moving back isn't an easy option as the job market I left sucks.How come I can't move on from my break up?
tough situation, the only thing that I can suggest is that you focus on your career right now and in your free time maybe get out and meet new people. don't keep yourself locked up in the house all day feeling sorry for yourself, you will never get over her if you do that. good luck.