Epictetus reiterates what makes us free or enslaved.
"If you want to preserve your choice and keep it in accord with nature, you'll be entirely safe; all will go smoothly; you'll have no trouble. If you want to safeguard those things that lie within your own power and are free by nature, and remain satisfied with those, what is left for you to worry about?" (v. 1-3, p. 74).
Socrates safeguarded what belonged to him - that which was in his power. Therefore, he could state, with confidence, "I've never committed any wrong whether in my private life or my public life."
But, if you are going to stretch your desires and aversions towards things outside your control, you will become enslaved to those very things. You'll weep, groan and beg and you will "be a slave ever afterwards" (v. 12, p. 75).
Each of us must "choose unequivocally and wholeheartedly to be either the one thing or the other, either free or slave, either educated or uneducated, either a fighting cock of true spirit or one without spirit, either one who will endure a rain of blows until death or one who'll immediately give up the fight" (v. 13, p. 75).
The real goal: "Ensure that my mind will be able to adapt itself to whatever comes about" (v. 21, p. 76).
If you cannot succeed at this, then your master will be "whoever has authority over anything that you're anxious to gain or avoid" (v. 26, p. 76).