I once had a small crush (maybe just an attraction) on a friend that I 100% did not want to pursue anything with. He was already dating someone that I also considered at least a friendly acquaintance, and she became my friend too.

I got over the crush easily without distancing myself. Here's the thing, though. I was honestly 100% motivated to get over it. You have to be honest with yourself if you are. If you're not, remove yourself from the situation (distance yourself physically).

Anyway, I find the the trick is to keep neutral. Don't make a big deal out of it in your head. Don't feel so gulty; it's just a crush. Feelings are not behaviors, and if you are wise about separating the two you have nothing to be guilty about.

More on being neutral: when you catch yourself daydreaming about him or whatever it is that you do (haha), just notice it, remind yourself it's okay but you don't want to be with him, and allow yourself to let it go. That's it.

Oh shit, he got a hot voice? Nice. Notice your thoughts. Accept it, maybe laugh it off a little if you want, tell yourself it's okay and then remind yourself you don't want to be with him, then allow yourself to let it go.

Oh damn, his WoW character is super powerful? That's neat haha. Notice it, accept it's how you feel, allow yourself to let it go.

Don't let it stew. Don't let fantasies or daydreams take over you without you gently reminding yourself that you intend to get over this. Remind yourself that physical attraction is just physical attraction. It's not a big deal unless you want it to be. Letting yourself get all excited about it and tempted and think about it all day and night is going to rev you up. If that happens, just gently remind yourself of these things.