Your ability to minimize the time spent in areas of decreased wind pressure or lulls on a race course will  improve your overall performance. It really helps if you can anticipate that your are coming into a lull. Often it can be seen on the surface of the water as a smooth area. If there are sailors ahead of you sometimes you’ll see them slow down or change angle. If the lull is large enough with a significant drop in pressure, you might consider tacking to try and avoid it. But often it’s a just temporary decrease in pressure that you’ll want to pass through as quickly as possible. So when you’re driving upwind and you see evidence on the water that you’re coming to a lull or begin to feel the pressure in the sail begin to drop, be ready to counter the resulting drop in speed by footing off slightly. This keeps the air moving across the sail attached and generating lift while also minimizing the amount of time spent in the lull, getting you to the good pressure again so you can resume your optimal VMG.