What sort of person are you? Do you put a lot of effort into helping others without much regard to what you gain in return from them? If so you are a person with high ‘communal orientation’ and people like you have been shown in new research to be generally happier than those with low communal orientation.
However people who do give a lot of their time to help their friends do still expect to count on them; but they run the risk that they will not be there when they do need a hand.
Take some time to read this interesting article as it will really get you thinking about your relationships.