I know you're hurting, and right now all you can think about is HER. And it seems like you're never going to get over it, like you're never going to find anyone better then HER. Its hard to understand how she can possibly be happy and you be so miserable...Its only normal to feel this way. It will take some time, but it will get easier. I promise. It takes time to heal from a break up, and it is a very painful process.
You will come to realize that its ok to have a few people who come into your life that will cause you to experience heartache, saddness, loneliness. Its those people who we love and never thought we could live with out that show us in the end who we were meant to be, give us strength to continue, and give us the knowledge of how to be better.
My grandmother's words of wisdom that have helped me through some of the hardest times in my life: "This too will pass."