Why is it best to push hardest when we feel lowest?

I worked early on in my career at a number of companies where I, for long stretches of time, was uninspired. I would go to work for eight hours a day and I would not be exercising the maximum of my capacity. I would not be stretching and reaching and firing my neurons in a way that would rebuild them faster. I was just plotting, or not plotting. That sounds devious. Just muddling through, and that muddling through I thought, "Do you know what? Work isn't super interesting right now. Work isn't super motivating, but then when I come home, I'll have all this extra energy."

That's not how it works. You can't save energy like that. In fact, you get energy by using energy. You get stronger by exercising your muscles. You get smarter by exercising your brain. It doesn't work to reserve it. I can't save the day. I was like, "Oh, I'm going to take it really easy today and then tomorrow or the next day I'm going to have that extra day." What? No. That day has passed. That energy just gets flushed. It gets wiped out. That sense of taking on responsibility, even when it's uncomfortable, even when you'd rather not is the source of meaning. I think for perhaps even most people most of the time, but it's such a difficult one to realize, particularly when you're starved for it. When you are in the dumps of it and there isn't enough and the energy is low, the last thing you think of is, "How can I spend more? How can I take on more," but that's exactly what you need to do.