From http://www.therealpresence.org/essentials/commandments/acc23.htm
Experience tells us that we develop moral habits according to our fidelity to the voice of conscience.
There is an iron law in the formation of habits. Apart from the supernatural action of divine grace, we can acquire good moral habits, called virtues, as we can acquire bad moral habits or vices. The law which underlines all formation of habit says that every thought tends to become a desire, every desire tends to become an action, and every action tends to become a habit.
Consequently, there is no such thing as a sterile thought. We conceive a thought and, unless checked, it grows into a desire. The same holds true of our desires. Unless checked, they become actions. And so, too, with actions. Simply because I have performed any action, interior or exterior, it spontaneously grows into a habit by sheer repetition.
Moral Virtues. Unlike the theological virtues of faith, hope, and charity, the moral virtues are immediately directed toward morally good actions. 1. Prudence enables us to make correct moral judgments. A prudent person can recognize what needs to be done, and what morally good means should be used to do what is pleasing to God. St. Thomas Aquinas teaches that prudence is composed of no less than eight elements: * the memory of past experiences on which a person draws when making a moral decision. * understanding of the basic principles of morality, derived from reason and revelation. * docility or the willingness to learn from others, especially those of mature age and experience. * shrewdness in being able to make a wise conjecture about the best course of action to follow in a particular case. * reason or the ability to apply general principles to a concrete situation. * foresight is the single most important part of prudence. The very word “prudence” means being able to provide or foresee how something should be