Real happiness seems to come from something like the Buddhist ideas of mindfulness and acceptance, and that's true whether you're a poverty-sworn monk, a janitor, a CEO, or a pot-smoking layabout.
The idea of "rewarding work" vs. "empty hedonism" is an arbitrary Western construct with little basis in reality.
That's not to say that working, alone, producing happiness is a correct idea, but it might make sense that accomplishment does. And these levels of accomplishment - cleaning the floor well for a janitor, for instance - can differ. Most people desire to "make a difference," another way of saying the same thing. If you're talking about deathbed wishes when looking back on a life, the more positive impact your life visited on others, the better.