Plato identified the four chief virtues as courage (sometimes fortitude), prudence (or wisdom), temperance (moderation), and justice. The virtues in this list were later named the four "Cardinal" virtues, distinquishing them from the "theological" virtues of faith, hope, and love as named by Paul in his letter to Corinth. (See Thomas Aquinas.)
First, that those who have virtues are strong. Their virtues give them their strength. Some seem to have only the virtue of physical strength, while others are stronger by having developed prudence or the other virtues.
I feel some ownership in this discussion, if only by virtue of my name, and so I offer my modifications to the list.
Faithfulness is being about your work. In the face of danger, faithfulness becomes the equivalent of courage; the faithful person is working despite the danger. The one who endures ennui without ending the effort is faithful; as is the one distracted by enthusiasm who does not depart from the assignment. Being faithful may sometimes seem equivalent to living a life of tedius attention to the task, but that is an illusion that comes from looking at the basement as if it were the entire house. The foundation holds the kitchen and the dining room and so makes the banquest possible. Faithfulness is an attribute of God and is emulated by God's people.
Discernment is the attention and the effort given to identifying the scope and nature of that assignment. The word is sometimes used to name the understanding which results from the success of this effort, and a "discerning" individual may refer to one who is frequently able to achieve a clear understanding. But I want to emphasize the virtue of making the effort. How well you see depends on the quality of your eyes, on how diligently you use them, and on how well you consider the images your eyes observe. Discernment is the analogous process of spiritual insight, and depends on gifts of grace and on faithfulness in using the gifts you have received.
Proportionality has the beauty of carrying connotations from mathematics and poetry and ethics. Proportionality allows an unlimited response to a boundless love or a quiet answer to an insignificant affront. It carries no hint of conforming to some gray middle ground. Proportionality requires careful discernment of the size and weight and flavor of every stimulus, for the response must be measured against the incitement.
Righteousness means to be full of the Right, which is to say being full of God. The righteous person is zealous for doing God's justice, which we've sometimes noted varies a bit from merely human notions of fairness and equity.