It is what it is... Is it?

What do you do when someone constantly asks you for favors and you help them without hesitation, when you see them in need and you lend them a helping hand with no questions asked, or even be their guardian angel and watch their backs all the time..

Yet all they did was to take things for granted? And when you require assistance or help for yourself from them and they refuse? Do you continue helping them or give up hope?

I don't know what to do anymore. It's been years. I am beginning to feel really drained. What to do.. Can anybody help me?