Not An Act But A Habit

Excellence is an art won by training and habituation: we do not act rightly because we have virtue or excellence, but we rather have these because we have acted rightly; "these virtues are formed in man by his doing the actions"; we are what we repeatedly do.  Excellence, then, is not an act but a habit.

-- William James Durant (1885 - 1981), American historian, philosopher, and writer, The Story of Philosophy (1926) p. 87.  The quoted phrases within the quotation are from Aristotle's Nicomachean Ethics, Book II, 4; Book I, 7