The Discourses of Epictetus, tr. by P.E Matheson, , at sacred-texts.com
The one thing to be careful about beyond all others is this—not to get so involved with any of your former companions or friends, as to compromise your character for his sake, for if you do this you will destroy yourself. If the thought slips in, 'I shall seem rude to him, and he will not be the same to me as before', remember that nothing is done without paying for it, and that it is not possible to be the same man that you once were, unless you do as you did before. Choose then which you will —to be like your former self and be loved as before by those who loved you, or to be better than before, and so miss what they once gave you. For if this is the better choice, then incline to this, and let no irrelevant arguments distract you, for no one can make progress by facing both ways. No; if you have chosen this course before all, if you wish to devote yourself to this and nothing else, and to spend all your labour on this, then dismiss all other thoughts, or else this facing both ways will produce a double result—you will not make progress as you ought, and you will fail to get what you got before; for before, when you frankly set your desires on worthless objects, you were agreeable to your companions. You cannot excel both ways; in proportion as you succeed on the one side, you must needs fall short on the other. When you do not drink with those whom you used to drink with, you cannot seem as agreeable to them as of old; choose then, whether you wish to be a drinker and gratify them, or sober and displease them. If you do not sing with those that you sang with, you cannot win their affection as before: here too then you must choose which you prefer. For if it is better to have self-respect and self-control, than to have it said of one, 'What a charming fellow!', then give up all other considerations, put them from you, turn away from them, and have nothing to do with them. But if this is not going to satisfy you, then turn round completely, and practise the very opposite—unnatural lust, adultery, and all that is in keeping with them, and you shall get what you want. Yes, jump up and shriek applause over your dancer.
But characters so opposite do not mix: you cannot act both Thersites
and Agamemnon. If you want to be Thersites you must be humpbacked and bald, if Agamemnon, you must be handsome and tall, and love your subjects.