By Aristotle (384-322 B.C)
Virtue, then, is of two kinds, intellectual and moral.
Intellectual virtue springs from and grows from teaching, and therefore needs experience and time.
Moral virtues come from habit…
They are in us neither by nature, nor in despite of nature, but we are furnished by nature with a capacity for receiving them, and we develop them through habit…
These virtues we acquire by first exercising them, as in the case of other arts.
Whatever we learn to do, we learn by actually doing it: men come to be builders, for instance, by building, and harp players, by playing the harp.
In the same way, by doing just acts we come to be just; by doing self-controlled acts, we come to be self-controlled; and by doing brave acts, we become brave…
How we act in our relations with other people makes us just or unjust.
How we face dangerous situations, either accustoming ourselves to fear or confidence, makes us brave or cowardly.
Occasions of lust and anger are similar: some people become self-controlled and patient from their conduct in such situations, and others uncontrolled and passionate.
In a word, then, activities produce similar dispositions.
Therefore we must give a certain character to our activities…
In short, the habits we form from childhood make no small difference, but rather they make all the difference.
Moral virtue is a mean that lies between two vices, one of excess and the other of deficiency, and… it aims at hitting the mean both in feelings and actions.
So it is hard to be good, for surely it is hard in each instance to find the mean, just as it is difficult to find the center of a circle.
It is easy to get angry or to spend money– anyone can do that.
But to act the right way toward the right person, in due proportion, at the right time, for the right reason, and in the right manner–this is not easy, and not everyone can do it.
(From the Nicomachean Ethics)