Don't. Seriously don't.
I had few long relationships. And by long a mean few years. That last one completely put me down. The girl was too perfect for me. I loved her too deeply and way too self-destructive. Yet I have no regrets. These 3 years made me so much better person then I ever was. So many things have changed.
One of the most important things I realized even tho all those years didn't quite work in the end. Only a bunch of people can say they felt that way. And it may sound immature but I have a few friends who got married, yet never felt so deeply in love with their fiance. They were never ready to sacrifice that much as I did. Me myself was in a few long relationship till then, where I had it all and almost got married and loved that girl, yet I felt that if that is all there is I would rather not sacrifice. But then that last girl. 3 years we tried to build something. She honestly tried too. But in the end she was never able to love me. She was honest tho and I always knew that. But me? I felt it all. I now understand all those fairy tales in movies and books, where main hero considers to save her instead of the whole world. And that feeling, even tho there is a lot of drama and tragedy attached to it - it's important. It's the most important feeling I had in my whole life. It's precious to me.
So please - give a fuck. As much as you can. If you really believe that you can't love stronger then you were. If you really think that it was IT. Even if the person who you felt it with is no longer around. And it's long over and cannot be ever restored. It doesn't matter much by now. What you feel is inside you, it's yours, it's very important. Majority of people even tho they may be more succesfull or somewhat better than you - never felt that way. If you had it - you are rare. If you had it you are rich. Feed off of it. It may lead to the greatest achievements in you life. And always remember - no matter how hard it is now, life is long enough, you never know how it may turn out in the end.