How can you stop caring about someone you love?

I still love my ex though we broke up a couple months ago. We had been together for three years and she ended it. There is not one day that I do not go without heartache or think about her, and I feel at this point it's detrimental and not good for me. How do I make myself indifferent, especially when I still have to see her every week? I'm a , I know, but I really feel for her. I just want to move on.