Man's faculties and functions are so interrelated that whatever affects one affects all. Athletes who over-develop the muscular system do so at the expense of the physical, mental, and moral well-being. It is a law of nature that the overdevelopment of any function or faculty, forcing or straining it, tends not only to ruin it, but also to cause injurious reactions on every other faculty and function.
Vigorous thought must come from a fresh brain. We cannot expect nerve, snap, robustness and vigor, sprightliness and elasticity, in the speech, in the book, or in the essay, from an exhausted, jaded brain. The brain is one of the last organs of the body to reach maturity (at about the age of twenty-eight), and should never be overworked, especially in youth. The whole future of a man is often ruined by over-straining the brain in school.
Brain-workers cannot do good, effective work in one line many hours a day. When the brain is weary, when it begins to lose its elasticity and freshness, there will be the same lack of tonicity and strength in the brain product. Some men often do a vast amount of literary work in entirely different lines during their spare hours.
Cessation of brain activity does not necessarily constitute brain rest, as most great thinkers know. The men who accomplish the most brain-work, sooner or later—usually later, unfortunately—learn to give rest to one set of faculties and use another, as interest begins to flag and a sense of weariness comes. In this way they have been enabled to astonish the world by their mental achievements, which is very largely a matter of skill in exercising alternate sets of faculties, allowing rest to some while giving healthy exercise to others. The continual use of one set of faculties by an ambitious worker will soon bring him to grief. No set of brain cells can possibly set free more brain force in the combustion of thought than is stored up in them. The tired brain must have rest, or nervous exhaustion, brain fever, or even softening of the brain is liable to follow.
As a rule, physical vigor is the condition of a great career. What would Gladstone have accomplished with a weak, puny physique? He addresses an audience at Corfu in Greek, and another at Florence in Italian. A little later he converses at ease with Bismarck in German, or talks fluent French in Paris, or piles up argument on argument in English for hours in Parliament. There are families that have "clutched success and kept it through generations from the simple fact of a splendid physical organization handed down from one generation to another."
William Ewart Gladstone
All occupations that enervate, paralyze, or destroy body or soul should be avoided. Our manufacturing interests too often give little thought to the employed; the article to be made is generally the only object considered. They do not care if a man spends the whole of his life upon the head of a pin, or in making a screw in a watch factory. They take no notice of the occupations that ruin, or the phosphorus, the dust, the arsenic that destroys the health, that shortens the lives of many workers; of the cramped condition of the body which creates deformity.
The moment we compel those we employ to do work that demoralizes them or does not tend to elevate or lift them, we are forcing them into service worse than useless. "If we induce painters to work in fading colors, or architects with rotten stone, or contractors to construct buildings with imperfect materials, we are forcing our Michael Angelos to carve in snow."