That shit is hard mate, I'm sorry. Break ups are a bitch, especially after a good long relationship. There is one of two things I would do. If I thought the breakup was not for a just reason, or I feel that the relationship didn't end correctly, I would ask her to talk. Sit down, have a long conversation on what happened and stuff. Or two, I try to exhaust myself through activities, so I don't have to really think about it, till eventually the feelings go away. This would mean, working, exercising (maybe a little excessively), reading, hanging with friends, etc.