The most important thing is that man should earn money through honest means only. Corrupt and underhand methods to earn money only demean and dehumanize a man and peace of mind eludes such a man.
So, if a man leads a simple, honest life, and is hard working, he can really live a happy life. Hard work is rightly said to be the key to success. One can find real happiness in work and nowhere else. One must be truthful, honest and brave. That is also essential for a happy, healthy life.