Can friend be trusted?

friend is aperson that very important in our life . As friend , we also help people in our life and need friends to help us in our life. After we help our friends , some of them try to ignore u. That feeling is so what , When they need help or they in helpless , we are willing to help them even we are in troble too just bacause of friend reelation ship . I just do not understand why this situation always happen in our life . I think we should not misuse our friend relationship for our own purpose .