Steps: how to let go

1. Realize that you still love this person. If it feels as if you can't let go, it's for a reason. Forgetting this person may be very hard to nearly impossible, but that doesn't mean that you can't move on in life.
2. Understand that there are other people out there, you just can't see them. You obviously have been in love with this person so much or so long that it has gotten you to the point where there's no other person in the world but them. Moving on is the hardest part and it can take a long time, but go out with friends and have a good time, because life is too short to live it down in the dumps.
3. Never love anyone more than they love you. This one may be hard because most chances are that the person doesn't know how deeply in love you are with them. Pretend you are in their position and realize how they feel... this should affect you because you would know what they're feeling about you.
4. Talk to someone. It's always good to get out your feelings with someone comfortably. Talk to someone close to you or if you have to, go see a therapist. Letting go of your emotions and thoughts with someone can be a natural healer. Know that you don't always have to cry it out. (Even though sometimes you have to).
5. Remain friends with the person. This is better than losing the person completely. Also, remaining friends can make you feel better. However, do this for the right reasons. If you are staying with them in the hopes that they may love you again, then don't. This could restrict you in life and cause you even more pain. Listen to your own heart.