Friendship

Friendship is a fluid concept. But given the fact that we invest so much time and energy in friendships, why is this the case? You can be friends with someone for years at a time, and then -flash- it's gone. One misstatement. Or, there are those friends that you invest so much time with, trying to "get" them; help them cope with their various issues. You try and try and try to understand these people, you try everything you can think of to help them, and they will not reciprocate. They persist in their state. When do you give up?