Crush for 7 years?

It's been 7 years and I can't get this guy out of my mind. I had a crush on this guy I met in my classes, we always greeted each other but never became friends or exchanged contact. But why I am still thinking about him? Sometimes it drives me crazy to not be able to handle my feelings for him, which has grown stronger over time without having any contact with him. What should I do?
Crush for 7 years?
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