She Went back to her ex, after 1 year

We dated for almost 1 year and she went back to her ex. when I met her, I wanted to marry her right away. But two month after we went out she told me that when she dated me, she was broken up with her ex two weeks before. It killed me to know or even think that I was a rebound. But I fooled myself.. Love is really blind, I helped her go through all the break up moments and get over him.. (since she opened up to me). But a year later when she saw him again, they started kissing and crying together.. It killed me to know that the girl that I could give the world to, just kissed another guy. I broke up with her, cause there was no reason when she can't love me and also can't get over her ex. God, it makes u really feel ugly and worthless.. It's been couple of weeks since, But I'm trying to read lots and lots of books on life and nature, It helps me undrestand life and know that It's not all about what You lost, it's about what's coming to you tomorrow.. So I'm trying to forget about her.. it's not easy but it's going to be done.. I just ask God to give the strenght for it.. Good Luck all you Guys that have your hearts broken.. remember, it's not you, and it's never you, it's just how life loves to play games with us and know that everything happenes for a reason..