"do only what is allowable"

"33. Set up right now a certain character and pattern for yourself which you will preserve when you are by yourself and when you are with people.  Be silent for the most part, or say what you have to in a few words.  Speak rarely, when the occasion requires speaking, but not about just any topic that comes up, not about gladiators, horse-races, athletes, eating or drinking -- the things that always come up; and especially if it is about people, talk without blaming or praising or comparing.  Divert by your own talk, if you can, the talk of those with you to something appropriate.  If you happen to be stranded among strangers, do not talk.  Do not laugh a great deal or at a great many things or unrestrainedly.  Refuse to swear oaths, altogether if possible, or otherwise as circumstances allow.  Avoid banquets given by those outside philosophy.  But if the appropriate occasion arises, take great care not to slide into their ways, since certainly if a person's companion is dirty the person who spends time with him, even if he happens to be clean, is bound to become dirty too.  Take what has to do with the body to the point of bare need, such as food, drink, clothing, house, household slaves, and cut out everything that is for reputation or luxury.  As for sex stay pure as far as possible before marriage, and if you have it do only what is allowable.  But do not be angry or censorious toward those who do engage in it, and do not always be making an exhibition of the fact that you do not."

-- Epictetus, The Handbook