How to stop liking a guy? Either that or asking him out?

I’ve liked a guy for three years now. He is amazing. He has never dated anyone before and right now I’m sure we are just friends. It kills me. We are both insanely busy people and I know that maybe it wouldn’t work out. I already know I’m not his type and that he deserves somebody happier and more stable; somebody smarter than me. I’ve tried everything and I still end up crying myself to sleep after writing a letter to him that I will never send. I need this to stop, really. If after two years of being friends one or the other has not said anything then I might as well find a way to make myself stop feeling so dizzy all the time, right? Help? Please?