Mencius said, "Once the Niu Mountain was covered with beautiful greenery, but since it was near a large city, it was attacked by lumberjacks. How could it retain its beauty? Still, by breathing in the sunlight and rain, how could new buds and sprouts not appear? But then cattle and sheep came and fed themselves, and by the time they were done, it was completely barren. When people see this barrenness, they imagine that there had never been any greenery. But is this the true nature of the mountain? Is it not also the way humanity is? How could they lose the mind of humaneness and integrity? The way in which humaneness and integrity are lost is like the way in which the trees are hewn down with axes and hatchets. As trees are cut down day after day, can a mountain retain its beauty? To be sure, the days and nights do the healing, and there is the nourishing air of the calm morning which keeps the mind normal in its likes and dislikes. But the effect is slight, and the mind is stifled by what is done during the day. When there is repeated disturbance, the restorative influence of the night will not be sufficient to preserve the goodness of the mind. When the influence of the night is not sufficient to preserve it, a man becomes not much different from the beast. People see that he acts like an animal, and think that he never had the original capacity for goodness. But is this his true character? Therefore, with proper nourishment and care, everything grows, whereas without proper nourishment and care, everything decays. When Confucius said: 'Use it and you will keep it; ignore it and you will lose it. No one knows the times of its coming or going, nor its direction,' he was talking about the mind."
Mencius (382-278 B.C.), Bk. I.