The Virtues then come to be in us neither by nature, nor in despite of nature, but we are furnished by nature with a capacity for receiving [them] and are perfected in them through custom.
Again, in whatever cases we get things by nature, we get the faculties first and perform the acts of working afterwards; an illustration of which is afforded by the case of our bodily senses, for it was not from having often seen or heard that we got these senses, but just the reverse: we had them and so exercised them, but did not have them because we had exercised them. But the Virtues we get by first performing single acts of working, which, again, is the case of other things, as the arts for instance; for what we have to make when we have learned how, these we learn how to make by making: men come to be builders, for instance, by building; harp-players, by playing on the harp: exactly so, by doing just actions we come to be just; by doing the actions of self-mastery we come to be perfected in self-mastery; and by doing brave actions brave.“
-Aristotle, Nicomachean Ethics