An archaeologist/attorney who had spent time on a kibbutz (not Jewish), John's answer is this:
being helpful to other people
When you strip away the false idols of material success and realize that they will just create an additional void and you see that "keeping up w/the Joneses is an exercise wheel in a gerbil cage," this will fill you with a sense of well being.
What do you think makes you happy, truly happy?