Shadows are tricky. I just happen to like them, so I've thought more about them than most people probably have. They *seem* evil. If you were to make a list up of all the worst qualities a person could possibly have and then made a character based on that -- that would be *your* shadow.
For example, I'm a very patient and honest person, so things in *my* shadow would be impatience and dishonesty. However, there are times when I am impatient. Instead of acting angry at all impatient people and feeling superior to them, I need to remember that there are times that I am also impatient. As for dishonesty, there are times when it really is the best thing. For example -- I now feel justified in calling in "sick" when I need (and truly need, not just pretend need) a mental health day. This isn't entirely honest, but my boss doesn't need to know about my mental problems/stress levels/way I manage stress.