By Aristotle

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.