To understand what the shadow is, we must understand different parts of our personality. According to Freud’s psychoanalytic theory, our personality is made up of the id, ego, and superego. The id is the unconscious and impulsive parts of our personality that correlates to natural urges and desires which developed the moment we are born. Unlike the id, the superego correlates to morals and values which develop as we grow older and learn about society's norms. The ego makes decisions by battling between the id and superego. The ego strives to make realistic decisions to satisfy the urges of the id without hurting the values of the superego.
So what is the "shadow"? According to Carl Jung, a Swiss psychiatrist, the shadow is the unconscious rejected parts of our personality. More specifically, these are the traits within ourselves that we reject because it contradicts with our ego/self-concept of ourselves.
For example, if a young boy strongly identifies himself with his gender, he will embrace everything that has to do with being a boy. This can include playing with cars, playing basketball, and watching action movies. Furthermore, he won’t watch or participate in any "girl" activities such as watching movies with lead girl characters or associating with the color pink. The important thing to note is that even if he has a natural urge to participate in girly activities he won't because he strongly identifies with being a boy. As a result, he is repressing the opposite of his identification. This leads to the development of the shadow. This does not mean that these are his true preferences, this means that he is limiting himself and his experiences because of his strong identification to being a boy.
As you can imagine, several problems can come from repression.
One of the problems that come from repression is that we will judge ourselves and others harshly. When we reject a trait of ours because it conflicts with the image of ourselves, we tend to judge others that obtain that trait harshly. Instead of acknowledging the fact that we obtain the trait as well, we reject that trait within ourselves and bring others down to elevate our ego.
So what should we do to get rid of our shadow? We should check in with ourselves daily and recognize when we judged others. We should also explore our judgment about others and ask ourselves if we that trait within ourselves. For example, if we see ourselves judging our lazy uncle maybe it’s because we have lazy tendencies ourselves and strongly reject them. After we identify that negative trait, we should convince ourselves that it is not a negative but a neutral trait. Continuing with this example, we would accept the fact that we are lazy at times which is why we judge our uncle harshly. Now we are going to tell ourselves that being lazy is okay; it is not a terribly bad or good thing.
As a result, working with our shadows and recognizing our negative traits will bring us closers to others, bring clarity in our lives, and prevent us from judging ourselves and others harshly.