"Lao Dan said, 'Be careful not to meddle with the human heart! The human heart is something that springs up when pushed down, sometimes ascending and sometimes descending, sometimes the prisoner and sometimes the executioner. How soft and restrained and pliable it is, yet how firmly and roughly and sharply and severely it chisels and cuts. So hot it smolders to fire, so cold it freezes to ice, so swift that in the interval between glancing up and glancing down it has already twice touched points beyond the four seas. It dwells still like an abyss, it moves like the overhanging heavens -- stampeding and haughty, allowing nothing to tie it down. Such is the human heart! ...'"  

               - Zhuangzi, translated by Brook Ziporyn, Hackett Publishing edition 2020