Finally someone who knows what they are talking about.
One of the first things my instructor told me when I started racing was that you should never be coasting! You should be either hard on the throttle or hard on the brakes!(Corner exit and sweepers excepted)
Another thing which was taught to me when I first started driving was that you should always be in the correct gear at all times - makes it easy to suddenly get back on the throttle in an instant and drive out of a situation if required. Easiest way to accomplish both of these is with heel-toe downshifting. I'm so used to doing it now that I do it without thinking in all manual vehicles I drive - even the old crappy column shift work van!