Good question. In practice, the way I see it the most "successful" people tend to be very busy, overloaded, stressed out, not exactly happy. On the other hand, I do know some people who live pretty simply life yet always seem to be in a good mood.
I guess it comes down to personality. For some people, the "sit back and relax" option isn't fun and does not make them happy.
The question of "What's best for society?" itself is quite loaded and may not be so trivial as it seems for first glance.
E.g. Does Bill Gates live a life that is good for society ?
- some people think so, because he made a hugely successful company and now supports various charities with his money
- however he made his money with rather questionable ethics, driving various other truly innovative companies into bankruptcy, so one can argue that without him, technology would have advanced faster (by other companies he killed), and the money would have been better "invested".