Nicomachean Ethics

You become what you repeatedly do

Earliest we can find

This is the earliest source we can find for the idea. Said again in 4 books on our list: Benjamin Franklin, Autobiography (1791), William James, The Principles of Psychology (1890), Will Durant, The Story of Philosophy (1926) and James Clear, Atomic Habits (2018).

1. “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.”