The closer you get to the Light, the more of your shadow you see. Thus truly holy people are always humble people. As one master teacher cleverly put it, “Avoid spirituality at all costs; it is one humiliation after another!” It could have been a great service to Christians if shadow had been distinguished from sin. Sin and shadow are not the same. We were so encouraged to avoid sin that instead many of us avoided facing our shadow, and then we “sinned” even more—while remaining unaware besides!

As Paul taught, “The angels of darkness must disguise themselves as angels of light” (2 Corinthians 11:14). Any idealized persona does not choose to see evil in itself, so it always disguises it as good. The shadow self invariably presents its own selfishness as something like prudence, common sense, justice, or “I am doing this for your good,” when it is actually manifesting fear, control, manipulation, or even vengeance. (The name Lucifer literally means the “light bearer.” The evil one always makes darkness look like light—and makes light look like darkness.)

Invariably when something upsets you, and you have a strong emotional reaction out of proportion to the moment, your shadow self has just been exposed. So watch for any overreactions or over-denials in yourself. When you notice them, the cock has just crowed (Mark 14:68)!

The reason that a mature or saintly person can be so peaceful, so accepting of self and others, is that there is not much hidden shadow self left. (There is always and forever a little more, however! No exceptions. Shadow work never stops.) The denied and disguised self takes so much energy to face, awaken, and transform that normally you have little energy left to project your fear, anger, or unlived life onto others.

from Falling Upward: A Spirituality For the Two Halves of Life

emphasis mine