Discourses, Against the Quarrelsome and Ferocious

Epictetus — The Slave

His goal is simple: while others do their own thing however they want, he stays true to his nature and lives according to it. He just does what's his to do so that others can also live according to their nature. This is what a wise and good person always aims for. Does he want to be a military commander? No. But if he's given that role, his goal is to keep his mind right while doing it. Does he want to get married? No. But if marriage happens, his goal is to stay true to his nature within it. But if he wants his son to behave or his wife to act right, then he's wanting something that belongs to someone else to not belong to them. The whole point of learning is this: figure out what's yours and what belongs to other people.

Epictetus — The Slave Original

but that while others are doing their own acts, as they choose, he may nevertheless be in a condition conformable to nature and live in it, only doing what is his own to the end that others also may be in a state conformable to nature. For this is the object always set before him by the wise and good man. Is it to be commander (a prætor) of an army? No; but if it is permitted him, his object is in this matter to maintain his own ruling principle. Is it to marry? No; but if marriage is allowed to him, in this matter his object is to maintain himself in a condition conformable to nature. But if he would have his son not to do wrong or his wife, he would have what belongs to another not to belong to another: and to be instructed is this, to learn what things are a man's own and what belongs to another.