I worked for a few years with a woman who was earning her degree in Marriage and Family Therapy. She wrote her dissertation on the Jungian theory of the Shadow Self. I had the opportunity to read only part of the paper, but we discussed the topic a few times and have read a bit on the subject. I understand the Shadow Self to be part of each person's psychological makeup. It is the part of ourselves we repress and deny. It is the dark side of our human nature.
Jung believed that we had to acknowledge and accept the shadow side as part of the whole of ourselves. Sometimes the overreacting to a person or situation is due to things you recognise in yourself that you don't like. They are outside your awareness and can be quite opposite of what you believe about yourself.
I have been told that I sometimes speak to people with a certain "tone" in my voice - that my words and the way I say them don't match. I don't hear it - I don't realize it unless it is pointed out - but more often people do not point it out, they are simply disturbed by it. This is apparently part of what broke down my relationships with some of my co-workers. I know I need to become more mindful of my emotions in order to remove this broadcasting of negative feelings. Not to hide them, but to be more direct in my communication.
I have searched my self and find that the issues I had were not with the individuals I worked with, but the frustration of not being able to do the work which satisfied me, that feed my ego. My frustration was coming out in my communication with people.
Those who know and love us, accept the good and bad. The dark and the light. Those who are irritated or repulsed by us are projecting onto us parts of themselves that they disown, that they deny. They will usually not identify with the projected quality or characteristic at all. It will be all about you - not them.
As things broke down at work, my co-worker became extremely sweet and nice to everyone but me. To me she was curt, dismissive and judgmental. Her niceness to others is a mask. And as Jung put it “Whatever one does not live, lives against one.”