How do I forget my ex girlfriend?

I've been and am very much in love with my current girlfriend of four years. Everything is great, except I often feel heart sore that I lost my ex everytime I think of her. This seems to be happening alot more lately and I'm starting to get a bit emo over the whole thing. I am a lesbian, so does this just mean girls have heightened emotions and I'm just stuck with it? Or do you have suggestions how to get over what I thought I had already/ dealing with it. Thanks guys xox