What is a happy life? It is peacefulness and lasting tranquillity, the sources of which are a great spirit and a steady determination to hold fast to good decisions. How does one arrive at these things? By recognizing the truth in all its completeness, by maintaining order, moderation and appropriateness in one’s actions, by having a will which is always well-intentioned and generous, focused on reason and never deviating from it, as lovable as it is admirable.
—Seneca Letters, 92.3