The shadow self, most commonly known as the "shadow", is a psychological concept defined by Carl Jung as the part of our psyche which encompasses all that we repress. This includes what we consider our defects, weaknesses, secret fears, emotional pain, instinctual impulses, and anything else we prefer to hide from others (and ourselves).
The shadow often displays behaviors which are opposite to what we normally express - characteristics which can be perceived as the "not me". It will, thus, contain traits that are as negative as any corresponding positive trait we exhibit in daily social interactions, particularly those which are excessive. For example, someone seemingly very extroverted may hide a shyness proportional to how excessive his expression, and need for expression, may be.
The shadow, however, is not our enemy - it can also contain many positive or useful traits which we are hesitant to allow ourselves to properly tap into. As such, it contains a great deal of personal power and creativity which, once tapped, can be focused toward productivity and inner growth. Working with the shadow can be achieved through meditation, introspection, and dream analysis.
Guidance regarding the Shadow Self
The Shadow Dance - Understanding Repetitive Patterns in Relationships