When I signed a book deal in the middle of my PhD, I knew that I’d have to be very disciplined when it came to rest, so I did what most people would consider the “right” thing: I took regular breaks and went to bed early. On paper, I was doing everything you’re supposed to do to protect your energy. And yet, I kept feeling tired. It didn’t make sense, so I started looking into it, and what I found is that most of us are working with the wrong model of energy management. We tend to think of personal energy like a battery: We use it up, and then recharge by doing nothing. But biologically, energy behaves less like a battery and more like a machine: It doesn’t automatically repair itself just because you stop using it. It might sound counterintuitive, but doing less can actually make you feel more tired. The mistake is assuming that feeling tired means you just need to do less. Sometimes that helps.…