Carl Gustav Jung

The shadow is a tight passage, a narrow door, whose painful constriction no one is spared who goes down the deep well. But one must learn to know oneself in order to know who one is. For what comes after the door is, surprisingly enough, a boundless expanse full of unprecedented uncertainty, with apparently no inside and no outside, no above and no below, no here and no there, no mine and no thine, no good and no bad. It is the world of water, where all life floats in suspension; where the realm of the sympathetic system, the soul of everything living, begins; where I am indivisibly this and that; where I experience the other in myself and the other-than-myself experiences me.
-Carl Gustav Jung