The common theme from this chapter seems to be "mental toughness."
A person has to be really mentally tough to stand up to a tyrant and bully. Mental toughness begins with the ability to derive contentment from within. If you think you will be content by obtaining or avoiding things external to your mind, you will be disappointed. As Epictetus says, "If you want something good, get it from yourself."
If you are able to gain contentment from yourself, then what can a tyrant do to you? A tyrant may threaten to put you in chains, but he is not putting you in chains; rather he is putting your hands in chains. A tyrant may threaten to lop off your head, but he is not killing you, he is killing your body. Indeed, Epictetus is using some very extreme examples to make a point. The modern-day equivalent is a saying that kids may say to a bully: "sticks and stones may break my bones, but words will never hurt me."
A tyrant or bully ultimately wants complete control over you - they want to control your judgments, your opinions, your thoughts. But this is where the tyrant loses control. He does not have this power. He may have power to chain you, imprison you or kill you, but he can never control your thoughts. But what about mind-altering drugs? Well, then, that falls under the category of controlling your body (your brain), but the real you is not under his control.
Another aspect of mental toughness is to have patience with those who are not philosophical. If you, as one who studies philosophy, have decided that true, meaningful happiness cannot be found in the opening of Christmas presents; and if a child comes up to you, to wish you a Merry Christmas, you do not begin to philosophize and say that Christmas is not "good", rather you should say, "Merry Christmas" back to the child. Similarly, if you cannot persuade another person to change their perspective on philosophy, then treat them as you would a child who lacks understanding and context - be patient with them (see verses 30-32).
Once we have learned something, we should be willing to practice it. We should always be ready for and looking for opportunities to practice virtue. "We should keep all this in mind, then, and when we're summoned to confront any difficulty of this kind, we should know that the moment has come to show whether we have received a proper philosophical education ... Athletes ... are non too happy to be matched against lightweights" rather they want a challenge to test their practice and learning (see v. 33-35, p. 65-66).
Furthermore, you can view people who "don't get it" as opportunities to practice what you learn from philosophy. Are you up to the challenge of being patient with others? Why did you read and study these things (Stoicism) if not to practice it? You should be grateful for chances to demonstrate what you've learned, and disappointed when you don't have an opportunity to practice. Gladiators begged to be put in the coliseum with worthy opponents - they were always eager to prove their mettle (see verses 36-38).
Developing mental toughness also requires you to embrace and love the life you've been given. We do not get to choose our circumstances all the time. We do not get to choose who our parents and family are. You have the ability to cope and live in contentment now, in these circumstances. Just like clothes and props don't make an actor great (it's his acting that makes him great), so too it is not our circumstances that make us happy; it's how we react to them that does! Are you or can you be a philosopher as a Senator or Emperor? How about as a garbage collector? Epictetus makes a call to everyone: "What is it that is lacking, then? Someone to put them into practice, someone to bear witness to the arguments in his actions" (verse 56).