I've been thinking a bit about a quote I posted the other day... the gist of it is:
"Being a giver can create a feeling of meaningfulness, while being a taker often generates a feeling of happiness."
Meaningfulness might equate to an increase in self esteem... the idea that we feel better about ourselves when we help others. Happiness, in this case, would be being the recipient of the good will of another.
Not the end all be all of the human experience, but interesting nonetheless.