On the Manual of Epictetus, aka The Enchiridion, from around 135 CE.
What's a wise strategy for life? What is freedom? Stoicism says that the secret is mastering yourself. If you let yourself be perturbed by things that happen to you, then you're a slave to those external things. Your good lies only in the things you can (with practice) control, i.e., your own attitudes, judgments, and opinions. Even a slave can be free, according to this strategy: Nothing external can break your spirit unless you let it.
The full four are joined by comedian Alex Fossella of the Modern Day Philosophers podcast to argue about how weird and misguided Epictetus's advice actually is. Read more about the topic and get the book.
Epictetus image by Sterling Bartlett.