What is happiness?
The happy are happy in possessing the good, and there’s no need for us to ask why men should want to be happy.
Plato, Symposium, 204e.
He is happy who lives in accordance with complete virtue and is sufficiently equipped with external goods, not for some chance period but throughout a complete life.
Aristotle, Nicomachean Ethics, 1101.a.10.
Man wills happiness of necessity, nor can he will not to be happy, or to be unhappy.