Sometimes we try too hard to make certain people a part of our lives that really don't want to be there. It takes a lot of effort on our part without positive results. As hard as it is, sometime it's better to let the person go and move on with our lives. It will hurt, but the pain will lessen, and hopefully someone else will help fill the gap you've been trying to fill with the wrong person.
I think this happens a lot- we expect more from others because we would be willing to do that much for them. Unequal relationships lead to bitterness and anger. Taking the time to talk with someone about your expectations and their expectations can help clear up misunderstandings. If both are willing to compromise and work out a new solution, it can open up a path for a beautiful relationship.