The man employed at work for which he is unfit, therefore, finds it not a means of self-expression, but a slow form of self-destruction.  All this wretchedness of spirit reacts directly upon the efficiency of the worker.  “A successful day is likely to be a restful one,” says Professor Scott,—­“an unsuccessful day an exhausting one.  The man who is greatly interested in his work and who finds delight in overcoming the difficulties of his calling is not likely to become so tired as the man for whom the work is a burden.

“Victory in intercollegiate athletic events depends on will power and physical endurance.  This is particularly apparent in football.  Frequently it is not the team with the greater muscular development or speed of foot that wins the victory, but the one with the more grit and perseverance.  At the conclusion of a game players are often unable to walk from the field and need to be carried.  Occasionally the winning team has actually worked the harder and received the more serious injuries.  Regardless of this fact, it is usually true that the victorious team leaves the field less jaded than the conquered team.  Furthermore, the winners will report next day refreshed and ready for further training, while the losers may require several days to overcome the shock and exhaustion of their defeat.

“Recently I had a very hard contest at tennis.  Some hours after the game I was still too tired to do effective work.  I wondered why, until I remembered that I had been thoroughly beaten, and that, too, by an opponent whom I felt I outclassed.  I had been in the habit of playing even harder contests and ordinarily with no discomfort—­especially when successful in winning the match.

“What I have found so apparent in physical exertion is equally true in intellectual labor.  Writing or research work which progresses satisfactorily leaves me relatively fresh; unsuccessful efforts bring their aftermath of weariness.

“Intellectual work which is pleasant is stimulating and does not fag one, while intellectual work which is uninteresting or displeasing is depressing and exhausting....

“To restore muscular and nerve cells is a very delicate process.  So wonderful is the human organism, however, that the process is carried on perfectly without our consciousness or volition except under abnormal conditions.

“Food and air are the first essentials of this restoration.  In-directly the perfect working of all the bodily organs contributes to the process—­especially deepened breathing, heightened pulse, and increase of bodily volume due to the expansion of the blood vessels running just beneath the skin.

“Here pleasure enters.  Its effect on the expenditure of energy is to make muscle and brain cells more available for consumption, and particularly to hasten the process of restoration or recuperation.

“The deepened breathing supplies more air for the oxidation of body wastes.  The heightened pulse carries nourishment more rapidly to the depleted tissues and relieves the tissues more rapidly from the poisonous wastes produced by work.  The body, the machine, runs more smoothly, and few stops for repairs are made necessary.