I can't get this girl out of my mind...am I going crazy?

She is new in the office...a tempo. I don't really know her. We just say hi. I seldom see her in the office because we are in different floors. Lately, I have been thinking about her and no matter what I do, I can't get her out of my mind. She is pretty but I know girls who are more beautiful than her and they don't mess up my mind. But this girl is driving me crazy. Wherever I am, I think of her, whatever I do, I think of her. Arrrrgghhh! This has got to stop. What do I do?