If I told the details it might be identifying so I'll keep it generalized. I met someone who was nice to me but not interested in me but I didn't know that. I fell completely in love and obsessed painfully and constantly. This went on for years. I was both joyously happy and miserable when I thought about this person which was my every waking thought for such a long time.

It was hard after a while when I knew nothing could develop. I still kept fantasizing. But as the years passed and I met other people (to fantasize about) and other things happened, I gradually thought about the person less. Until one day it was just over.

You will meet other people and you'll become interested in someone else eventually.