@Deb This is a really good animation of various defensive driving techniques and do's and don'ts. He's extremely forgiving of what many would call a double move, and just gives you the reality of racing; Nothing is black and white. There is no such thing as "You need to be this far along side....". Its racing, and everything is fluid.
His very last sentence is great, and I think everyone should have it sticky-noted to their monitor in front of them at all times, whether you're attacking or defending! Every situation you're going to have to know your skill, make a best guess as to how the person racing you is going to drive, and then decide how much you're willing to risk in order to take or defend the position.