Discourses: Book 4 12 : 3
First, therefore, we ought to have these principles at command, and to do nothing apart from them, but keep the soul intent upon this mark; we must pursue none of the things external, none of the things which are not our own, but as He that is mighty has ordained; pursuing without any hesitation the things that lie within the sphere of the moral purpose, and all other things as they have been given us. And next we must remember who we are, and what is our designation, and must endeavour to direct our actions, in the performance of our duties, to meet the possibilities of our social relations. We must remember what is the proper time for song, the proper time for play, and in whose presence; also what will be out of place; lest our companions despise us, and we despise ourselves; when to jest, and whom to laugh at, and to what end to engage in social intercourse, and with whom; and, finally, how to maintain one's proper character in such social intercourse. But whenever you deviate from any one of these principles, immediately you suffer loss, and that not from anywhere outside, but from the very nature of the activity.