Laudator Temporis Acti

Arrian, Discourses of Epictetus 2.18.1-4 (tr. W.A. Oldfather):

Every habit and faculty is confirmed and strengthened by the corresponding actions, that of walking by walking, that of running by running. If you wish to be a good reader, read; if you wish to be a good writer, write. If you should give up reading for thirty days one after the other, and be engaged in something else, you will know what happens. So also if you lie in bed for ten days, get up and try to take a rather long walk, and you will see how wobbly your legs are. In general, therefore, if you want to do something, make a habit of it; if you want not to do something, refrain from doing it, and accustom yourself to something else instead.

πᾶσα ἕξις καὶ δύναμις ὑπὸ τῶν καταλλήλων ἔργων συνέχεται καὶ αὔξεται, ἡ περιπατητικὴ ὑπὸ τοῦ περιπατεῖν, ἡ τροχαστικὴ ὑπὸ τοῦ τρέχειν. ἂν θέλῃς ἀναγνωστικὸς εἶναι, ἀναγίγνωσκε· ἂν γραφικός, γράφε. ὅταν δὲ τριάκοντα ἐφεξῆς ἡμέρας μὴ ἀναγνῷς, ἀλλ' ἄλλο τι πράξῃς, γνώσῃ τὸ γινόμενον. οὕτως κἂν ἀναπέσῃς δέκα ἡμέρας, ἀναστὰς ἐπιχείρησον μακροτέραν ὁδὸν περιπατῆσαι καὶ ὄψει, πῶς σου τὰ σκέλη παρα λύεται. καθόλου οὖν εἴ τι ποιεῖν ἐθέλῃς, ἑκτικὸν ποίει αὐτό· εἴ τι μὴ ποιεῖν ἐθέλῃς, μὴ ποίει αὐτό, ἀλλ' ἔθισον ἄλλο τι πράττειν μᾶλλον ἀντ' αὐτοῦ.