[Note: you post is intentionally poetic, so I'll let myself be intentionally poetic while answering this:]
Would you trust someone without a shadow?
The correct answer is, I think, "don't care". On Friday night you dance with a Gervais-sociopath. On Saturday you build a moon rocket together and use it to pick up groceries. Do you "trust" the rocket to be "good"? No, but you don't need to.
The trust you have to have is that the person you are building with won't take the partially built rocket and and finish it for themselves to go off to a gambling den. That they too actually want to get groceries and aren't just saying that they do to gain your cooperation. You want to avoid cursing their sudden but inevitable betrayal.
You do want to get the groceries right?
I wrote last time that Jung's approach to humility deserves its own post:
Modern men cannot find God because they will not look low enough.
Here's the first piece of that post.
Look low enough by confronting the darkness in your personal hell.
Humility demands that you fix the problems in your own mind and life before trying to save the world. It is necessary to inspect the lens before you examine the territory. It is necessary to develop competence and purity of heart in humbler realms before seeking world-changing power. The world will fight you with everything it has - a single crack in your own defenses is mission-critical.
All of these are good reasons to conquer your own shadow. Would you trust someone without a shadow?
Here are two more essential reasons to take care of yourself and conquer your shadow before, or at least concurrently with, embarking on a heroic mission.
The first is that you will learn the power of attention by staring straight into the abyss. There is a handicap attached to this: every danger you leave unattended gets worse. Like gasses, shadows grow to fill the space they're in.
The second is another rule of Jung, that the Golden Rule is symmetric. Treat yourself with the respect a human being deserves.
Shadow is Gaseous
This post from Jessica Taylor brought this exquisite detail from Christopher Alexander to my attention:
The implication is that public spaces must be designed around the fundamental psychological drive to protect your back. Anything behind your back, you cannot watch. Its threat level shoots through the roof. For all you know, every tree, boulder, and passerby behind your back is tiptoeing towards you, knife in hand, waiting for you to let down your guard.
[Necessary trigger warning] SCP-173 is the first horror in the game SCP: Containment Breach. SCP stands for Secure, Contain, Protect.
Now that you're in the right mood, here's an invigorating exercise Jordan Peterson taught me. Find yourself a closed door to a dark room. Turn around with your back against the door, push it open just a crack, and slide your hand through the crack without looking. Watch your imagination as it populates the room with threats.
Psychological shadows are like SCP-173. As long as you keep your eyes on them, they are awful but manageable. Blink for too long, or turn your back, and the threat skyrockets. Every week you put off that dreaded task, it magnifies and looms in your imagination until you are crippled by anxiety and can't even leave the house.
I posted for the first time to LessWrong about a week ago after a much protracted inner struggle. The shadow had grown so tall as to induce a minor panic attack. It sent me circumambulating my apartment complex for half an hour, even though System 2 expressly and consciously expected the response to be uniformly positive.
Much of the dread is in your imagination. I cannot enumerate the number of crippling anxieties and addictions which, when I finally mustered my attention and cast a light on it, vanished in a puff of smoke and mirrors like the Wonderful Wizard of Oz.
Here's the secret of exposure therapy and comfort zone expansion: this startling contrast between light and dark is due to man's dual nature as predator and prey.
With your back to the enemy, it is predator and you are prey. It expands, amorphous and slippery as many-headed and many-limbed Cthulhu, to fill all the darkness you cede to it. If it leaps, it leaps in every direction you can imagine. Each step you flee leaves more space behind your head you are blind to. The shadow will steal every inch.
With your eyes on the enemy, you are predator and it is prey. It shrinks to a point: it is this exact defined thing, and not every possible threat. If it leaps, it leaps in one direction you can predict. If you cautiously but resolutely make the approach the shadow will shrink away, often to nothing.
Take heed, traveler: conquer the shadow while it's young.
The Golden Rule Runs Both Ways
Here is the standard formulation of the Golden Rule:
Treat others the way you want to be treated.
Plenty of people would benefit from this standard formulation, but there also some who treat themselves too poorly. Jung reminds these self-sacrificing souls that the Golden Rule runs both ways:
Treat yourself the way you would treat others.
I will return to this second idea in another post, and take it to its logical conclusion.