It is in everybody's interest to seek those [actions] that lead to happiness and avoid those which lead to suffering. And because our interests are inextricably linked, we are compelled to accept ethics as the indispensable interface between my desire to be happy and yours.
You will not rightly call him a happy man who possesses much; he more rightly earns the name of happy who is skilled in wisely using the gifts of the gods, and in suffering hard poverty, and who fears disgrace as worse than death.