Objection 1. It seems that daring is not a sin. For it is written (Job 39:21) concerning the horse, by which according to Gregory (Moral. xxxi) the godly preacher is denoted, that "he goeth forth boldly to meet armed men [Vulgate: 'he pranceth boldly, he goeth forth to meet armed men']." But no vice redounds to a man's praise. Therefore it is not a sin to be daring.
Objection 2. Further, according to the Philosopher (Ethic. vi, 9), "one should take counsel in thought, and do quickly what has been counseled." But daring helps this quickness in doing. Therefore daring is not sinful but praiseworthy.
Objection 3. Further, daring is a passion caused by hope, as stated above (I-II, 45, 2) when we were treating of the passions. But hope is accounted not a sin but a virtue. Neither therefore should daring be accounted a sin.
On the contrary, It is written (Sirach 8:18): "Go not on the way with a bold man, lest he burden thee with his evils." Now no man's fellowship is to be avoided save on account of sin. Therefore daring is a sin.
I answer that, Daring, as stated above (I-II, 23, 1; 55), is a passion. Now a passion is sometimes moderated according to reason, and sometimes it lacks moderation, either by excess or by deficiency, and on this account the passion is sinful. Again, the names of the passions are sometimes employed in the sense of excess, thus we speak of anger meaning not any but excessive anger, in which case it is sinful, and in the same way daring as implying excess is accounted a sin.
Reply to Objection 1. The daring spoken of there is that which is moderated by reason, for in that sense it belongs to the virtue of fortitude.
Reply to Objection 2. It is praiseworthy to act quickly after taking counsel, which is an act of reason. But to wish to act quickly before taking counsel is not praiseworthy but sinful; for this would be to act rashly, which is a vice contrary to prudence, as stated above (Question 58, Article 3). Wherefore daring which leads one to act quickly is so far praiseworthy as it is directed by reason.
Reply to Objection 3. Some vices are unnamed, and so also are some virtues, as the Philosopher remarks (Ethic. ii, 7; iv, 4,5,6). Hence the names of certain passions have to be applied to certain vices and virtues: and in order to designate vices we employ especially the names of those passions the object of which is an evil, as in the case of hatred, fear, anger and daring. But hope and love have a good for this object, and so we use them rather to designate virtues.
Source: Summa Theologica (New Advent)