In his book, Burns talks about a problem endemic even to to-do-list makers. He calls it do-nothingism, and says that like its close relative, procrastination, it's rooted in defeatism (the belief that your efforts won't get you anywhere), feeling overwhelmed ("It's all too much," you think), and fear (of disapproval, of success, of failure, or of not getting it "just right").

I saw, now, that "I don't feel like it" was my version of do-nothingism. Given that so many of the to-dos on my list were ruled by other people's needs or whims, "I don't feel like it" was my attempt at invoking some do-as-I-please autonomy. But if Burns was right in saying that action often leads to motivation and energy—and not the other way around—then my stubborn refusal to engage was only getting in my way.

That insight led me straight to Jim Loehr, coauthor of The Power of Full Engagement: Managing Energy, Not Time, Is the Key to High Performance and Personal Renewal. I liked Loehr's definition of engagement: "the ability to bring your full and best energy to whatever one is doing at the moment—right here, right now." And I felt a perverse glee when he told me, "People start getting less efficient at producing and recovering energy around age 25 or 30." (Depressing but validating; maybe I wasn't too young to be exhausted, after all!)

What I didn't like so much about Loehr's ideas, at least at first, was that he's a big "exercise, eat right, get a good night's sleep" guy. But as we talked, I started to see his point. A higher energy dividend, he said, comes with properly earning and spending the get-up-and-go currency that we call oomph, pep, zest, or "the juice." According to Loehr, the energy cycle breaks down this way: Make it, use it, replenish it, repeat. Twenty-minute walks and leafy green vegetables were "make it" endeavors. Six hours of sleep instead of three were replenishment.

And where I usually messed up—as Loehr told me most of us do—was in the "use it" cycle. Loehr blames the underuse of energy for much of the world's exhaustion. The biggest underuse culprit: being in a sedentary position for long periods of time. As in, ahem, watching TV.