If friends disappoint you over and over, that's in large part your own fault. Once someone has shown a tendency to be self-centered, you need to recognize that and take care of yourself; people aren't going to change simply because you want them to.
And though thou notest from thy safe recess old friends burn dim, like lamps in noisome air love them for what they are; nor love them less, because to thee they are not what they were.
We poets would die of loneliness but for women, and we choose our men friends that we may have somebody to talk about women with. Letter to Olivia Shakespeare, 1936
The glory of friendship is not the outstretched hand, not the kindly smile, nor the joy of companionship; it is the spiritual inspiration that comes to one when you discover that someone else believes in you and is willing to trust you with a friendship.