Why can't I can't stop fantasizing!?

I have a huge crush on my coworker and I think about her all the time. It is driving me nuts! She gives mixed signals. She smiles at me, talks to me often and touches or hugs me sometimes. Then other times she just walks right past me and doesn't say a word. She drives me crazy! She is insanely beautiful and no way would fall for a guy like mel!! My mind and body says that I must be with her but I know that I can't. Please give me some ideas to get her off my mind!