Objection 1. It would seem that the daring are not more eager at first than in the midst of danger. Because trembling is caused by fear, which is contrary to daring, as stated above (1; 44, 3). But the daring sometimes tremble at first, as the Philosopher says (De Problem. xxvii, 3). Therefore they are not more eager at first than in the midst of danger.
Objection 2. Further, passion is intensified by an increase in its object: thus since a good is lovable, what is better is yet more lovable. But the object of daring is something difficult. Therefore the greater the difficulty, the greater the daring. But danger is more arduous and difficult when present. It is then therefore that daring is greatest.
Objection 3. Further, anger is provoked by the infliction of wounds. But anger causes daring; for the Philosopher says (Rhet. ii, 5) that "anger makes man bold." Therefore when man is in the midst of danger and when he is being beaten, then is he most daring.
On the contrary, It is said in Ethic. iii, 7 that "the daring are precipitate and full of eagerness before the danger, yet in the midst of dangers they stand aloof."
I answer that, Daring, being a movement of the sensitive appetite, follows an apprehension of the sensitive faculty. But the sensitive faculty cannot make comparisons, nor can it inquire into circumstances; its judgment is instantaneous. Now it happens sometimes that it is impossible for a man to take note in an instant of all the difficulties of a certain situation: hence there arises the movement of daring to face the danger; so that when he comes to experience the danger, he feels the difficulty to be greater than he expected, and so gives way.
On the other hand, reason discusses all the difficulties of a situation. Consequently men of fortitude who face danger according to the judgment of reason, at first seem slack, because they face the danger not from passion but with due deliberation. Yet when they are in the midst of danger, they experience nothing unforeseen, but sometimes the difficulty turns out to be less than they anticipated; wherefore they are more persevering. Moreover, it may be because they face the danger on account of the good of virtue which is the abiding object of their will, however great the danger may prove: whereas men of daring face the danger on account of a mere thought giving rise to hope and banishing fear, as stated above (Article 3).
Reply to Objection 1. Trembling does occur in men of daring, on account of the heat being withdrawn from the outer to the inner parts of the body, as occurs also in those who are afraid. But in men of daring the heat withdraws to the heart; whereas in those who are afraid, it withdraws to the inferior parts.
Reply to Objection 2. The object of love is good simply, wherefore if it be increased, love is increased simply. But the object of daring is a compound of good and evil; and the movement of daring towards evil presupposes the movement of hope towards good. If, therefore, so much difficulty be added to the danger that it overcomes hope, the movement of daring does not ensue, but fails. But if the movement of daring does ensue, the greater the danger, the greater is the daring considered to be.
Reply to Objection 3. Hurt does not give rise to anger unless there be some kind of hope, as we shall see later on (46, 1). Consequently if the danger be so great as to banish all hope of victory, anger does not ensue. It is true, however, that if anger does ensue, there will be greater daring.
Source: Summa Theologica (New Advent)