I have a confession, I just learned what this meaning was recently, the shadow self. And this discovery of the word makes complete sense. Not only do I feel that it is extremely beneficial for our well being to address the shadow self and work with it but also to accept it as an asset. Think about it as the Star Wars saga - you see a hero that works with his inner teacher but faces the darkness. It's the yin and yang of who we are.
I'll be the first to admit that there is a secret side to myself that can be conceited and self rightous. WE all have an inner struggle with what we know can be mean, ugly, jealous, and so forth however our good angel, the one that knows and understands what is morally good.
"Carl Jung stated the shadow to be the unknown dark side of the personality. According to Jung, the shadow, in being instinctive and irrational, is prone to psychological projection, in which a perceived personal inferiority is recognized as a perceived moral deficiency in someone else."
So what can we do to work with our shadow self and harness that side of us that is nasty and dark? Turn it into something tangible like art or change that energy and thought. I tell people all the time that the jewelry I create, the aggressive talons, the large and possessed pieces reflect the badass part of me - the side of me that is unhindered.
I once read the performer and singer, Marilyn Manson say that his music channeled his aggression and violent thoughts however it didn't mean he went out and tried to do any violence to others. And I felt that it resonates so much with why it is so important to release certain energies and thoughts into good action.
thus - make art, dig in the dirt, go for a thrill seeking bike ride through your neighborhood, go to a ropes course with a friend, do some yoga, meditate, climb a tree, go swimming in the ocean - physical movement or activity stimulates some of the same chemicals in our brains as those found in certain drugs.
I hope this gave you some insight and thoughts about the shadow self and learning from all the aspects of yourself. The good and the bad.