Vital power is renewed in sleep. Every living thing sleeps; men, animals, reptiles, fish, and insects sleep, and even plants have regular periods of slumber. And this is because it is in sleep that we come into such contact with the Principle of Life in nature that our own lives may be renewed. It is in sleep that the brain of man is recharged with vital energy, and the Principle of Health within him is given new strength. It is of the first importance, then, that we should sleep in a natural, normal, and perfectly healthy manner...FROM THE BOOK