This is not so much an asshole situation as it is simply wrong expectations. Either that, or making an asshole of yourself in your own mind, if you will. 😜
One thing I've learned about giving my time and effort to others is not expect reciprocation of generosity, else I'll end up feeling exactly as you described: bitter and resentful. These days, when I do something kind, I expect nothing in return whatsoever, and it's kept any good deeds I perform completely honest. It also removes any ego from the good deeds, knowing that I'm doing them just for the sake of doing them, rather than as a point of pride.
Don't take this as a sign to stop doing good deeds, but rather to evaluate which ones matter the most to you.