The Enchiridion (Version 2) 6 : 1

Be not elated at any advantage (excellence), which belongs to another. If a horse when he is elated should say, I am beautiful, one might endure it. But when you are elated, and say, I have a beautiful horse, you must know that you are elated at having a good horse. What then is your own? The use of appearances. Consequently, when in the use of appearances you are conformable to nature, then be elated, for then you will be elated at something good which is your own.