Book XI · 4
Have I done something for the general interest? Well then, I have had my reward. Let this always be present to thy mind, and never stop [doing such good].
Have I done some social act? Well, I am amply rewarded. Keep this truth ever ready to turn to, and in no wise slacken thine efforts.
Marcus Aurelius, Meditations XI.4. Translated by George Long (1862). The Stoic Library.