ervous energy spent in this way
cannot be used in doing useful work, but must be counted as so much loss
to the body. One who would use his nervous system to the best advantage
must find some way of preventing waste of this kind.(108)

Undue excitement, as well as pleasurable dissipations, also tend toward
nervous exhaustion. And while the fact is recognized that pleasurable
activities supply a necessary mental exercise, the limit of healthful
endurance must be watched and _excesses of all kinds avoided_. Intense
emotional states are found to be exhausting in the extreme; and the
suppression of such undesirable feelings as anger, fear, jealousy, and
resentment are of immense value in the hygiene of the nervous system.

*The Habit of Self-control.*--Much of the needless waste of nervous energy,
including that of worrying over trivial matters, may be prevented through
the exercise of self-control. From the standpoint of the nervous system,
the present age differs from the past mainly in supplying a greater number
and variety of nerve stimuli. Self-control means the ability to suppress
activities that would result from undesirable stimuli and to direct the
bodily activities into channels that are profitable. Self-control,
therefore, is not only to be exercised on occasions of great emergency,
but in the everyday affairs of life as well. It is even more important
that the daily toiler at his task be able to keep the petty annoyances of
life from acting as irritants to his nervous system than that he keep cool
during some great calamity. The habit of self-control is acquired mainly
through the persistent effort to prevent any and all kinds of petty
annoyances from affecting the nerves or the temper.

*Nervousness.*--Self-control is much more easily practiced by some than by
others. This is due partly to habit, but is also due to an actual
difference in the degree of sensitiveness, or irritability, of the nervous
systems of different people. One whose nervous system tends to respond too
readily to any and all kinds of stimuli is said to be "nervous." This
condition is in some instances inherited, but is in most cases due to the
wasteful expenditure of nervous energy or to the action of some drug upon
the body. Excess of mental work, too much reading, long-continued anxiety,
eye strain, and the use of tea, coffee, alcohol, tobacco, or other drugs,
including many of those taken as medicines, are known to cause
nervousness. Ner