If you're heels are dragging, you usually have a solid edge, then nothing...total washout. You might be able to feel the boots dragging "in your heels" a moment before. If you've simply past the angle/speed the board can handle for your riding and conditions, there's usually board chatter just before it cuts loose. Good advise above. It will bring your center of gravity closer to board and give more downward pressure and less outward. It allows more responsive course corrections and recovery, too.