By exercising one can increase endurance, strength, and efficiency which basically gives you the ability to do more work and have more "energy". I wonder if there's a way to do the same with one's work energy. Are there ways of "working out" to increase your capacity over time to GTD? If I get 10 things crossed off my next actions list that's a big day for me. My average is around 4 at work and 4 at home. Are there ways to build up my next action fitness levels and do more in the same amount of time, like how a runner builds up to doing a marathon?