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.