How do these virtues help us?

According to Saint Thomas Aquinas, every decision we make is influenced by:

Thought, because the decision is usually the end product of a thought that is ultimately put into action.  The virtue of prudence divinizes our thoughts, raising them to a level that actually transcends our humanity.

Act, because a decision that is not acted upon is rendered ineffectual and incomplete, a waste of time.  The virtue of justice divinizes our actions.  Because we live lives of grace, more and more will we act like God.  We increasingly act in conformity with the will of Christ because of the ontological change bestowed on us through the grace of Jesus Christ.

Affection for those things we like doing.  The virtue of temperance divinizes affection.  That which is human in us channels our affections toward ourselves.  That is not good for us because it is not God's way.  Our affections have to be controlled because they play an important role in our decision-making.

Aversion for those things we don't enjoy doing.  The virtue of fortitude divinizes aversion.  Many of the decisions we make are determined by things we like or don't like.