Why is it so hard to move on from her?

I was rejected by a girl i really like. She liked me too but then she decided to end things. We kissed few times, went out and we were getting closer and closer. I thought it is just matter of time before we will be in relationship. But didn't happen. I am getting really sick of these mindf@cking thoughts. I’ve not moved on yet. I dont know what i did wrong. I still think of it and i can't stop even when i want so badly. All the time it is about what i did wrong, what i could have done better, what made her lose interest, that imagination she is with someone else kills me. Why it is so hard?

Why is it so hard to move on from her?
Post Opinion