Love is a mystery emotion. What I can tell you about it though is that you have to work at it daily. Most the time people do not know how much they love someone until that person is gone.

As for your ex-girlfriend, she will only come back when she is ready. if you stalk her, you will drive her away. I have found that most need their space and time to heal. In the meantime send her flowers, gifts, love notes, poems, and anything you can get your hands on that says "I am an idiot and I should have never let you go" that you can send to her.

And grovel at her feet.