The Enchiridion, Section 33 — In Plain English

Epictetus — The Slave

Start by deciding what kind of person you want to be. Then stick to that character whether you're alone or with others.

Stay quiet most of the time. When you do speak, say only what's necessary and keep it short. You can join conversations sometimes when it makes sense. But don't talk about the usual stuff — gladiators, horse races, athletes, food, or drinks. These are shallow topics. And especially don't gossip about people by criticizing them, praising them, or comparing them. If you can steer the conversation toward better topics, do it. If you're stuck with strangers who won't budge, just stay quiet.

Don't laugh too loud, too often, or too much.

Avoid making oaths if you can. At least try to avoid them as much as possible.

Epictetus — The Slave Original

Begin by prescribing to yourself some character and demeanor, such as you may preserve both alone and in company.

Be mostly silent, or speak merely what is needful, and in few words. We may, however, enter sparingly into discourse sometimes, when occasion calls for it; but let it not run on any of the common subjects, as gladiators, or horse races, or athletic champions, or food, or drink—the vulgar topics of conversation—and especially not on men, so as either to blame, or praise, or make comparisons. If you are able, then, by your own conversation, bring over that of your company to proper subjects; but if you happen to find yourself among strangers, be silent.

Let not your laughter be loud, frequent, or abundant.

Avoid taking oaths, if possible, altogether; at any rate, so far as you are able.