Epictetus, Enchiridion 17:
“Remember that you are but an actor in a play, and it is as the author wills it: should the author want a short one, it will be short, and should the author want a long one, it will be long. Should they want you to play the beggar, or a disabled person, or a ruler, or a commoner, try to act your part well. This is your business in life: to act well the part given to you. The choice of that part belongs to another.”
μέμνησο, ὅτι ὑποκριτὴς εἶ δράματος, οἵου ἂν θέλῃ ὁ διδάσκαλος: ἂν βραχύ, βραχέος: ἂν μακρόν, μακροῦ: ἂν πτωχὸν ὑποκρίνασθαί σε θέλῃ, ἵνα καὶ τοῦτον εὐφυῶς ὑποκρίνῃ ἂν χωλόν, ἂν ἄρχοντα, ἂν ἰδιώτην. σὸν γὰρ τοῦτ᾽ ἔστι, τὸ δοθὲν ὑποκρίνασθαι πρόσωπον καλῶς: ἐκλέξασθαι δ᾽ αὐτὸ ἄλλου.