Why can't I just......?

forget her? A few years ago whilst at University I secretly fell in love with a girl. We both used to look at each other but never said anything.I once met her and introduced myself but that was the end of it.She just blushed and from then on she used to run away whenever she see's me.I just couldn't understand why she did that.I am quite good looking,polite and really well mannered. We are no longer at university and it's been 3 years but I think of her everyday.This really upsets me and makes me sad.Any advise would be much appreciated.Thanks everyone.