The Enchiridion, Section 1 — In Plain English

Epictetus — The Slave

The things you control are naturally free, unlimited, and unblocked. The things you don't control are weak, dependent, limited, and foreign to you. Remember this: if you think you should be free to control things that depend on others, or if you treat other people's business as your own business, you will be blocked. You will complain. You will be upset. You will blame both gods and people. But if you claim only what is truly yours and see everything else for what it really is, then no one will ever force you to do anything. No one will limit you. You won't blame anyone. You won't accuse anyone. You won't act against your own will. No one will hurt you. You won't have enemies. You won't suffer any harm.

Epictetus — The Slave Original

Now the things within our power are by nature free, unrestricted, unhindered; but those beyond our power are weak, dependent, restricted, alien. Remember, then, that if you attribute freedom to things by nature dependent and take what belongs to others for your own, you will be hindered, you will lament, you will be disturbed, you will find fault both with gods and men. But if you take for your own only that which is your own and view what belongs to others just as it really is, then no one will ever compel you, no one will restrict you; you will find fault with no one, you will accuse no one, you will do nothing against your will; no one will hurt you, you will not have an enemy, nor will you suffer any harm.