I came across this article that describes really well what our shadow(according to Carl Jung) is and does to us. I'll post a short portion of what this article talks about and if you're interested you could keep reading from the link given. I'll be interested in further discussion if you guys are up for it.
Full article: http://www.shadowdance.com/shadow/theshadow.html
.We have all had experiences with other people that really irritate us. Whenever we feel ourselves over-reacting emotionally to a quality or characteristic in someone else that pushes all of our buttons (and there will be a repulsive element to it), we can be sure that we are seeing a part of our own Shadow.
We will not be able to stand this other person or be around them at all. The reaction is usually extreme distaste as these characteristics or qualities that we despise or hate in others are our own and they are usually operating outside of our awareness. They are in our unconscious and usually they will be the exact opposite of what we believe to be true about ourselves.
Now a person carrying a light part of our Shadow we will be very drawn to, and may even fall in love with, and this is the ‘Gold’ part of our Shadow. So we can also project some of our very positive qualities when we meet someone we truly admire, but most of us have more trouble with the negative experiences as we encounter our Shadow. This is the psyche’s way of bringing itself into the light meaning the light of consciousness
Full article: http://www.shadowdance.com/shadow/theshadow.html