This may be a chicken and egg conundrum. Are they happy because they socialize; or do they socialize because they are happy?

The same goes for altruism. Is one altruistic because they are happy; or are they happy because they are altruistic?

Off the top of my head (with no deep thought to this) I suspect that if one is unhappy with their life, altruism will not make them happy with their life. They may still get the "warm glow", but not the deeper happiness.

I agree with you. I don't give in order to get thanks, accolades or praise from the recipient or from those who witness my giving. I much prefer to give anonymously in private.

I sense a continuum here. From the warm glow to resentment or bitterness, with various stages of "good" and "bad" feelings along the continuum. I have no problem with give until in hurts, if the hurt is that I have to deny myself something relatively unimportant or delay gratification for something. For example handing my brown bag lunch to a hungry homeless person is painful, especially once the hunger sets in, but I realize that my hunger is much less than his. This certainly won't make me angry or bitter. The challenge is for each of us to find our own place along this continuum.