Picture, one version of a map of how Jung sees the human.
The light part is all you control and know.
Dark part (Animus, or animal self) is all that is automatic, outside of your control.
Ego is who you think you are, the Shadow is who you really are.
The dark part is only changed by experiences and emotions, not by ideas and beliefs.
So the shadow is made only of what you experienced and felt, not by anything you believe.
Therapy in its ideal form is meant to do 2 things: Know ourselves, dig into that dark area and understand it/ourselves, and to be able to change it somehow to be able to enjoy life better and get rid of misunderstandings and unnecessary burdens.

Most modern therapy is ineffective because of the rejection of the metaphysical/religion language/thinking, they actively try to remove the metaphysical of the mind and make things even worse.

Save for Jung and a few other psychologists that understood the mind cannot be mapped/cognized by current science.