No hagas que tu felicidad dependa de lo que no depende de ti - Epictetus

Never call yourself a philosopher, nor talk a great deal among the unlearned about theorems, but act conformably to them. Thus, at an entertainment, don’t talk how persons ought to eat, but eat as you ought.

If, however, I liberate myself from my master – which is to say, from the emotions that make my master frightening – what troubles can I have? No man is my master any longer.

In literature, too, it is not great achievement to memorize what you have read while not formulating an opinion of your own.