Thomas Aquinas

“ But fear incites to counsel more than hope does. Because hope is of good things, as being possible of attainment; whereas fear is of evil things, as being difficult to repel, so that fear regards the aspect of difficulty more than hope does. ”

“ The stronger a passion is, the greater the hindrance is it to the man who is swayed by it. Consequently, when fear is intense, man does indeed wish to take counsel, but his thoughts are so disturbed, that he can find no counsel. If, however, the fear be slight, so as to make a man wish to take counsel, without gravely disturbing the reason ”

“ I answer that, Man's exterior actions are caused by the soul as first mover, but by the bodily members as instruments. Now action may be hindered both by defect of the instrument, and by defect of the principal mover. ”

“ In fear, heat abandons the heart, with a downward movement: hence in those who are afraid the heart especially trembles, as also those members which are connected with the breast where the heart resides. Hence those who fear tremble especially in their speech, on account of the tracheal artery being near the heart. ”

“ He that falls from a plank placed aloft, suffers a disturbance of his imagination, through fear of the fall that is pictured to his imagination.
Reply to Objection 3: Everyone in fear shuns that which he fears: and therefore, since laziness is a fear of work itself as being toilsome, it hinders work by withdrawing the will from it. But fear of other things conduces to action, in so far as it inclines the will to do that whereby a man escapes from what he fears. ”

“ And it is in matters of difficulty, especially when we distrust ourselves, that we take counsel, as stated above.
Art. 3 - Whether fear makes one tremble? Objection 1: It would seem that trembling is not an effect of fear. Because trembling is occasioned by cold; thus we observe that a cold person trembles. Now fear does not seem to make one cold, but rather to cause a parching heat: a sign whereof is that those who fear are thirsty, especially if their fear be very great, as in the case of those who are being led to execution. Therefore fear does not cause trembling. ”