Find avenues to channel those feelings away from yourself and observe your reaction to it. Sample, ask a friend to keep you busy or occupied and observe when he passes by and when you got more occupied to your friend, then there is a chance that you can beat that infatuation. But if you observe that it get's worst when diverted, try approaching the guy and be honest with him, whatever his reaction is, it will make you feel better in the long run or instantly.
Or... you can listen to emo songs and slash your wrist and be a douche.