Best passage on swing:

“A good swing does not necessarily make crews go faster, … rowers get more bang for their buck on each stroke. Mainly what it does is allow them to conserve power, to row at a lower stroke rate and still move through the water as efficiently as possible, and often more rapidly than another crew rowing less efficiently at a higher rate. It allows them to possess a reserve of energy for a gut-wrenching, muscle-screaming sprint at the end of a race. … But the closer a crew can come to that ideal— maintaining a good swing while rowing at a high rate— the closer they are to rowing on another plane, the plane on which champions row.”

Brown, Daniel James (2013-06-04). The Boys in the Boat: Nine Americans and Their Epic Quest for Gold at the 1936 Berlin Olympics (p. 162). Penguin Group US. Kindle Edition.

This is what David Allen is talking about! Not only hitting your stride in doing GETTING THINGS DONE, but also a sense of effortlessness in the doing. It has taken me a LONG TIME to pull in enough skills just to employ crappy GTD. But every year it gets better. And every tweak of my GTD system is another stepping stone.