Hippocrates

"Everything in excess Is opposed by nature."

"For if a man by magical arts and sacrifices will bring down the moon, and darken the sun, and induce storms, or fine weather, I should not believe that there was anything divine, but human, in these things, provided the power of the divine were overpowered by human knowledge and subjected to it."

"In whatever disease sleep is laborious, it is a deadly symptom; but if sleep does good, it is not deadly."

"Natural forces within us are the true healers of disease."