Cant get over her

I had a girlfriend about two years ago. We were perfectly happy together and as far as I know, loved each others company. We shared many common intrest and could always find something to talk about and laugh. Then, suddenly, one day she broke up with me. I've had girlfriends since then but I never can get her out of my head for some reason. I see her everyday at school and while were just friends, I just still can't understand why she did that. Is this normal?
Category General Confession