=The Emotions Again.= What is the key that unlocks new stores of energy and drives away fatigue?  What is it in the amateur mountain-climbers that helps the body maintain its new standard?  What keeps indefatigable workers on the job long after the ordinary man has tired?  Is it not always an invigorating emotion,—­the zest of pursuit, the joy of battle, intense interest in work, or a new enthusiasm?  All great military commanders know the importance of morale.  They know that troops can stand more while they are going forward than while running away, that the more contented and hopeful they are, the better fighters they make; discouragement, lack of interest, the fighting of a losing game, dearth of appreciation, futility of effort, monotony of task, all conspire in soldier or civilian to use up and to lock up energy which might have been available for real work.  Approaching the matter from a new angle, we find once more that the difference between strength and weakness is in many cases merely a difference in the emotions and feeling-tones which habitually control.

Fatigue is a safety-device of nature to keep us within safe limits, but it is a device toward which we must not become too sensitive.  As a rule it makes us stop long before the danger point is reached.  If we fall into the habit of watching its first signals, they may easily become so insistent that they monopolize attention.  Attention increases any sensation, especially if colored by fear.  Fear adds to the waste matter of fatigue little driblets of adrenalin and other secretions which must somehow be eliminated before equilibrium is reestablished.  This creates a vicious circle.  We are tired, hence we are discouraged.  We are discouraged, hence we are more tired.  This kind of “tire” is a chemical condition, but it is produced not by work but by an emotion.  He who learns to take his fatigue philosophically, as a natural and harmless phenomenon which will soon disappear if ignored, is likely to find himself possessed of exceptional strength.  We can stand almost any amount of work, provided we do not multiply it by worry.  We can even stand a good deal of real anxiety provided it is not turned in on ourselves and directed toward our own health.

="Decent Hygienic Conditions."= If fatigue products cannot pile up, why is extra rest ever needed?  Because there is a limit to the supply of fuel.  If the fat-supply stored away for such emergencies finally becomes low, we may need an extra dose of sleeping and eating in order to let the reservoirs fill again.  But this never takes very long.  The body soon fills in its reserves if it has anything like common-sense care.  The doctrine of reserve energy does not warrant a careless burning of the candle at both ends.  It presupposes “decent hygienic conditions,”—­eight hours in bed, three square meals a day, and a fair amount of fresh air and exercise.