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.