Discourses, To the Administrator of the Free Cities Who Was an Epicurean

Epictetus — The Slave

But grief is something that depends on your will — that's an evil. Someone else bears condemnation with courage. That depends on their will — that's good. If we train ourselves this way, we'll make progress. We'll never agree with anything unless we can clearly understand what actually happened. Your son is dead. What happened? Your son is dead. Anything else? No. Your ship sank. What happened? Your ship sank. A man was taken to prison. What happened? He was taken to prison. But the idea that this is terrible — everyone adds that from their own opinion.

Epictetus — The Slave Original

Affliction is a thing which depends on the will: it is an evil. He has borne the condemnation bravely. That is a thing within the power of the will: it is a good. If we train ourselves in this manner, we shall make progress; for we shall never assent to anything of which there is not an appearance capable of being comprehended. Your son is dead. What has happened? Your son is dead. Nothing more? Nothing. Your ship is lost. What has happened? Your ship is lost. A man has been led to prison. What has happened? He has been led to prison. But that herein he has fared badly, every man adds from his own opinion.