This one will short and sweet and to the point...
Have you noticed that you can do and try to be everything for someone but the moment you can't or don't, you immediately become the bad guy? Why is that? What makes people forget all of the positive and helpful things you have done the mere second you have to say no? Everything that you've done suddenly...means nothing!
Have we as a society become so selfish that EVERYTHING has to benefit us? You have to remember the world doesn't revolve around you. People are out here suffering, homeless, hungry, and helpless. So if you have someone that genuinely cares for and about you, is willing to help you, and shows compassion for you, don't push them away when you can't get your way. And definitely don't throw it in a person's face the one time they can't provide for you or grant your wish.
Good people are hard to find nowadays. If you have a few of them in your life, KEEP THEM!