Reading your comments, I think you have super human level of energy. Not to take anything away from your experience, but that isn't much help to the OP who is likely much lower energy. I observe the same in myself. Each year that I age up, the gap in energy between myself and peers grows larger. They keep getting fatter, slower, lazier, less innovative/intelligent. Me: Yes, a bit, but far slower than others around me. The last five years has been striking -- the distance. More and more people ask me: "How do you do it?" Or "When will you slow down?". For years, I thought something was wrong with me and my brain. Now, I understand the gap better. To be clear: This does not mean that I am _absolutely_ smarter than my peers (or a better worker!) -- I am only talking about "energy levels". Ask yourself: How does Elon Musk work 80/90/100 hours per week in his early 50s? Probably a lot cocaine and caffeine. Plus, he has super human level of energy. When I listen to Cal Newport's style of working, I think: "Oh, hey, that's me!" Of course, I'm not a university professor and successful author of many best sellers. But the energy level is similar.

what is your take on caffeine consumption?