I have a stupid work crush too *highfives* Made all the more stupid by the fact that I don't want to be thinking about this other person because I'm already in a completely happy relationship.

My usual strategy to deal with such things is to tell the person (sometimes not a fun thing to do), it gets the crush out of the way and things tend to return to normal. I think it's because when you tell someone you have a crush on them either they reciprocate, or they let you down which sort of deflates the stupid elation you get from seeing them.