Aristotle BOOK II: developing a virtue of character vs developing a skill

The developing a virtue of character similar to developing a skill or art in the following ways:

First, we acquire the virtue and the knowledge of the skill by using it, but before we used them, we have already had them. For example, before we practice playing tennis, the coach told us how to use the rackets and how to hit the ball. While we practise, we gradually apply the theory we learnt from the coach to the exercise. Finally, we became skilled tennis players. It is the same with the virtue. We know what courage is before we do the courage actions. Meantime, when we do the courageous actions, our courage increased and we became courageous people. On the contrary, if we do not practice in a correct way, slightly we may become bad tennis players or the discourage people.

Second, akin to developing a skill or art, the origin and means of the development of each virtue are the same as those of its corruption, but the activities that flow from them will consist of the same things. Because of the correct and scientific practice strategy, he became an outstanding tennis player. As a consequence, he could be most able to practice most efficiently. Another example is the temperate. We became temperate owing to our abstaining from pleasure. As we became temperate, we are most able to abstain from pleasure.

However, these two processes have differences. Of developing a virtue, agents don't have to own the virtue's worth in them, but just do the actions. Nonetheless, for developing a skill, the players have to absorb all the knowledge in their own mind. For instance, we may describe a person as temperate because he does temperate actions. Nevertheless, we can't describe as a tennis player just because he was playing tennis. Besides, two more things are required and playing important roles in developing a virtue, one is the agent acts in a certain state from rational choice and rational choice of the cautions for their own sake; one is the certain state from a firm and unshakeable character. Those two characteristics are absent in developing a skill.