So you are saying that you need some sort of personal gain (ticket to an utopian afterlife for example) to be a nice person?
Btw, even taking a very atheistic perspective, only focused on how humanity evolved (which is a selfish process in spite of your future protestations of how you have trascended it) we can see we evolved to be nice only out of self-preservation.
One would think that is the ultimate personal gain but I'll grant you that reminding yourself you are a good person must be a psychological gain of its own.