For what we do in our dealings with other people makes some of us just, some unjust; what we do in terrifying situations, and the habits of fear or confidence that we acquire, makes some of us brave and others cowardly...To sum it up in a single account: The State of Character Results from the repetition of Similar Activities. That is why we must perform the right activities, since differences in these imply corresponding differences in the states
From Nicomachean Ethics, BookII,Ch.2:Virtue of Character, 1103b