I have noticed that every time I take a shot since I got my camera a couple of months ago it has made me much more conscious about lighting, especially shadows. I tend to look at shadowed areas as things to avoid in the shot, and how to frame a scene to avoid them.
Now looking back at some of my work, and looking through other photography portfolios, I have seen my error in judgment. It's not about avoiding them, but actually utilizing them effectively in the capture to bring them in, to fit the shot or scene. So my new mission is to try and start getting some captures that make use of dim lighting and natural shadows more, and force myself to use them as a tool rather than a hazard to avoid.