Chapter 6 of the Manual of Epictetus

Do not take pride in a good feature that is not really yours. It is still bearable if a horse would say of itself: 'I am beautiful'. But when you say proudly, "I have a beautiful horse," then realize that you are boasting about something that belongs not to you but to your horse. What then belongs to you? Your character. Whenever you live in accordance with nature, you can be proud of yourself. Then you are proud of a quality that really belongs to you.

Today, Epictetus would probably have taken a car as an example. Just as our holy cow is used as a status symbol, a beautiful horse was seen as a sign of prosperity in Antiquity. Epictetus warns his students not to make the mistake that the possession of beautiful and expensive stuff means that you are also a good and happy person. The value judgment that someone with many possessions is also better than someone who is less wealthy is simply nonsense.

Stoics try to stimulate positive feelings and avoid negative emotions as much as possible. Being proud of the stuff you own seems innocent, but that's not true. It can be a source of disturbing feelings of envy. Your neighbour can become jealous of your beautiful car and start treating you differently out of jealousy. Even worse, you run the risk of becoming envious yourself if your neighbour, in response to your purchase, acquires an even better and bigger car. Jealousy is an unpleasant emotion and Epictetus wants to protect his students as much as possible from such unnecessary feelings. If you want to live a happy life, it is a risky business to be proud of your possessions.

According to Epictetus, pride is not a bad quality under all circumstances. As long as you make a good distinction between the qualities that really belong to you and the qualities that belong to something or someone else. You can be proud of something that really belongs to you. Being proud of the beauty of your car is actually a bit ridiculous. The only thing that car say's about you as a person is that you have enough money in your bank account to make an expensive purchase. It is something external, something that is strange to you as a person and that you have no control over. What really matters is your inner beauty, the things that you have control over. It concerns your character, what you do, your way of life and not your possessions. Your character is the only thing that truly and completely belongs to you. According to Epictetus, you can only be proud if you succeed in leading a good and happy life.