If I'm limited to picking a "skill," then it's moving with the ski all the time. Like most "advanced amatuers," I spend far too much time toward the back of the ski or otherwise disconnected. But if I get to pick more general terms, then it's much easier: Dedication. Even a decade ago when I was working hard on getting better, I always recognized there was an entirely different level of dedication possible, with nutrition, coaching, off-water training, and consistent, purposeful on-water training.