While it is true that one should not let fear hold him back from duties and useful actions, we must remember that fear is a natural instinct and as such, is bound to have useful functions for the preservation of species and individuals. To understand this, we enumerate some of the emotions belonging to the fear complex: caution, apprehension, sense of danger, fright, terror and panic.
All of these feelings may be displayed by a herd of gazelles or deer living in constant danger from the onslaught of fierce predations. Only speedy flight saves the herd from extinction. There, the smallest unusual noise makes the animals cautious; a faint smell of the predator causes apprehension; the loud roar of a lion means imminent danger and sends the entire herd into rapid flight. If, however, the aggressor is recognized as one who may be resisted, such as a coyote, a wolf, or a mountain lion, a dominant male may be aroused to fight rather than flight; the excitement of danger secretes adrenalin into its veins, readying it for either action.
When a powerful aggressor is in the midst of the herd, panic is dispersed through uncontrolled random flight. This reduces the density of the group and thus the danger to each individual. The old, sick, and feeble are most likely to be devoured, so that the average quality of the herd is improved by survival of the fittest.
Even paralysing terror has its value for survival. Many predators such as spiders, and some snakes, have poor eyesight and can notice only moving objects. A fly is safe from a spider as long as it remains immobile.
Paralysing terror can save human lives at the onset of a severe heart attack. The pain of such an attack may be violent, but the chief terror of angina pectoris (literally ‘constriction of the chest,’) is the instinctive anticipation of suffocation or heart failure. Under such conditions, immobility may save a victim’s life by conserving the scant supply of blood and oxygen until emergency aid can be given.
On the other hand, many patients remain frightened long after the physical damage is repaired. They and other excessively tense people suffer angina spasms at every incident, be it severe or trivial, that triggers reactions of fear, frustration, or resentment. For such people, the instinctive fear reaction has lost its survival value and has turned into a dangerous burden. In these cases, the danger caused by fear is not external but psychosomatic. The anguish of angina is brought on less by the mental strain itself than by worrying about it.
He who has overcome instinctive fear, who remains calm and confident in the midst of difficulties and provocations, is well on the road to mastery.
Extracted from the article The Dangers and Benefits of Fear by Walter Albershein