The Moral Virtue of Prudence, also known under the names: Restraint, Moderation and Diligence, acts in our intellect. Our intellect, aided by Restraint and enlightened by God, can see the world as it is. We can also see clearly, how our relation to this world should be! Diligence lets our intellect see what is right to do!
Diligence is essential for us when we need to judge between actions regarding ourselves and others. We need to be able to judge rightly when observing self-interest versus public interest, for instance.
Restraint makes us capable to take in consideration other people's needs, not only ours. Thus we can see how this Virtue enables us to fight selfishness!
It is also easier for us to practice self-control, and we will know how to deal with things inside us or things that happen around us.
Restraint helps us combat the Vice of Gluttony, because practicing moderation we can exercise control over our appetites. This is the tool to help us control the desire to drink too much, for instance. We will be free from the slavery of alcohol and other obsessions..
It's very important for a Christian to exercise this Virtue, in order to understand better how to act, regarding morality or in any particular situation. With this Virtue acting freely in our Souls, we are able to handle all life situations well and we can make wise decisions, morally spoken also.
Diligent people get in less problems than people who are used to act before thinking. This does not mean that we cannot be spontaneous. It rather means that we are capable to discern in a matter of seconds when the situation in which we are asks for restraint.
This happens with the assistance of the Holy Spirit, who dwells in people who are righteous.