How can i stop this help!?

i really really like one of my guy friends. i did like him before but tried to stop and managed and then he got a gf but has now spilt up with her. the biggest problem why i should stop is because he basically went out with my best friend so i dont want to go out with him, i know some people dont think this is a problem but i wouldnt like to. but anyway, i found out from my best friend that he did actually like me at some point, he seemingly said that he liked me, then she said something like awww and he said really really really liked her. but now i like him again, we are better friends than we have ever been and dont want to stop speaking. like today i was going to a party where he would be there and i was getting so excited and whenever he puts a loveheart on msn or sends kisses when saying bye i like get erflies.. but yeah, back to the question. how can i stop liking him and only be friends?