Objection 1. It seems that the precept of the parts of fortitude are unsuitably given in the Divine Law. For just as patience and perseverance are parts of fortitude, so also are magnificence, magnanimity, and confidence, as stated above (128). Now we find precepts of patience in the Divine Law, as also of perseverance. Therefore there should also have been precepts of magnificence and magnanimity.
Objection 2. Further, patience is a very necessary virtue, since it is the guardian of the other virtues, as Gregory says (Hom. in Evang. xxxv). Now the other virtues are commanded absolutely. Therefore patience should not have been commanded merely, as Augustine says (De Serm. Dom. in Monte i), as to the preparedness of the mind.
Objection 3. Further, patience and perseverance are parts of fortitude, as stated above (128; 136, 4; 137, 2). Now the precepts of fortitude are not affirmative but only negative, as stated above (1, ad 2). Therefore the precepts of patience and perseverance should have been negative and not affirmative.
The contrary, however, follows from the way in which they are given by Holy Writ.
I answer that, The Divine Law instructs man perfectly about such things as are necessary for right living. Now in order to live aright man needs not only the principal virtues, but also the secondary and annexed virtues. Wherefore the Divine Law contains precepts not only about the acts of the principal virtues, but also about the acts of the secondary and annexed virtues.
Reply to Objection 1. Magnificence and magnanimity do not belong to the genus of fortitude, except by reason of a certain excellence of greatness which they regard in their respective matters. Now things pertaining to excellence come under the counsels of perfection rather than under precepts of obligation. Wherefore, there was need of counsels, rather than of precepts about magnificence and magnanimity. On the other hand, the hardships and toils of the present life pertain to patience and perseverance, not by reason of any greatness observable in them, but on account of the very nature of those virtues. Hence the need of precepts of patience and perseverance.
Reply to Objection 2. As stated above (Question 3, Article 2), although affirmative precepts are always binding, they are not binding for always, but according to place and time. Wherefore just as the affirmative precepts about the other virtues are to be understood as to the preparedness of the mind, in the sense that man be prepared to fulfil them when necessary, so too are the precepts of patience to be understood in the same way.
Reply to Objection 3. Fortitude, as distinct from patience and perseverance, is about the greatest dangers wherein one must proceed with caution; nor is it necessary to determine what is to be done in particular. On the other hand, patience and perseverance are about minor hardships and toils, wherefore there is less danger in determining, especially in general, what is to be done in such cases.
Source: Summa Theologica (New Advent)