You ask what causes the shadow? As Robert Bly puts it in, 'The Long Bag we Drag Behind Us' in MEETING THE SHADOW:
'When we were one or two years old we had what we might visualize as a 360-degree personality. Energy radiated out from all parts of our body and all parts of our psyche. A child running is a living globe of energy. We had a ball of energy, all right; but one day we noticed that our parents didn't like certain parts of the ball. They said things like: 'Can't you be still?' Or 'it isn't nice to try and kill your brother.'
But if our parents weren't obsessed with sin and badness and had said 'Your activity is annoying me, would you take it elsewhere, or control it to please me?' instead of 'ADD is sick, oops 'Can't you be still?' If they said 'Your brother will hurt just like you do when hit, can you consider his feelings, that is use your natural empathy to identify with your potentially hurt brother?' Instead of 'It is sin to try to kill your brother.' Intervention may be necessary, but it is not necessary to dump a bunch of BS into the kid's bag during the intervention.
Wouldn't it be nice to be 25 with an empty bag? It can be done. When people try to dump BS into your bag simply say 'I don't need that. I can control that behavior, or do it where it won't annoy other people.' This is known as being socially responsible. Kids learn it naturally unless people dump BS into their bag.
When that little tinhorn in the fancy dress in the overdecorated balcony tries to dump his BS into my bag, I simply tell him that my BS bag has no bottom, and herm BS means nothing to me. Hesh will usually then scream 'God will send you to Hell sinner!'and I will smile nicely and say 'Hesh may try if Hesh wishes, but I doubt Hesh would as I am not a sinner. My BS bag is empty.'"
If people weren't loaded up with BS from the time they were 2 the shrinks and the preachers wouldn't have anything to work with. One of the most important things I learned early in life was the difference between "You are bad" and "Your behavior needs better control." I also learned very early that "You are bad" must for my own wellness be interpreted as "Fix your behavior." Fortunately I was encouraged to do so by my atheist parents, well technically Unitarian, I don't even know how they viewed God, but God and sin were not a part of my life growing up. As a result I don't have a bag full of BS to deal with particularly the BS about what I am. Contrary to popular belief this is neither unusual nor unbelievable.