Charles Wagner, “Effort and Work,” Courage (New York: Dodd, Mead and Company, 1903), pp.113-114:
A certain inertia, one might almost say an influence emanating from death, tends incessantly to neutralize and exhaust our vital force. Iron and steel rust; and every force, no matter what it may be, has beside it a principle of destruction which attacks it, and will ruin it unless it defends itself. Man is not exempt from this law. He must struggle against rust by regular exercise of his faculties. We are condemned by an inevitable law to advance unceasingly under penalty of falling into decay. Movement is not only a sign of life; it is a source of life. To strengthen his muscles, to carry his body, to learn to use his hands, his eyes, to become accustomed to fatigue, to the rigors of the seasons, to struggle against obstacles, to increase his intelligence by difficult exercise, to familiarize his will with opposition, to conquer his desires, his emotions, his passions, in a word, to tame and discipline his whole being. As soon as he applies himself to this task, which, I admit, is not without difficulty, he perceives how fortifying it is.