How do you get over someone you see all the time?

So I liked this guy. He's 20 and I'm 19. I actually thought he returned my feelings but I realized that I was disillusioned and he was only being nice. Problem is now I feel that he really hates me. Like it's as if he doesn't want to say hi. Sometimes he'll smile and say hi and other times, it's like I don't exist. I really want to get over him because I'm hurt. I just don't know how cuz I happen to run into him in church and school all the time. =[