Our coach likes 'True Lies' and is a good teacher I think. He likens facing bouncers and body-line to Tom Arnold (playing Albert 'Gib' Gibson) in True lies when he hides (foolishly) behind a very thin pole as bullets fly at his fat belly yet he stays unharmed, having checked his intact chest and genitals! In fact, he doesn't get hit because he stands so upright and perfectly side-on, thus presenting the smallest silhouette (or so the moral of the story goes). The converse being that as you step backwards you actually present more of yourself as a target. As has been mentioned before our coach puts a boundary cone behind your back foot if you have this unconscious tendency so as to make a conscious reminder. Besides if you're going to consider pulling it, it is better to step inside the line rather than away from it. Sorry it might not be anything new, but I like this analogy a lot, and bears repeating I think!