I am playing mind games with myself for few months now and I can`t get away fom them?

My mind plays games with me but it seems that I cannot stop that. Back in the time I used to date one gorgeous girl, but without saying anything, she got away from me. I don`t know what I did or if she was no more interested, but I waited for almost 3 months to get an explanation of what`s going on and during all those months my mind started playing games. Now it`s been almost a year and I still don`t get what I did wrong. Maybe I should just move on, but whatever I do, something always brings her up. ALWAYS and it`s just amazing why that happens. It was maybe the longest relationship that I had with a girl or which I though I had.