When I get tired, either at night or in the afternoon, it "feels" like it's my brain getting tired more than my body. It's harder to concentrate, make decisions, and see things clearly.
My core solution is pretty simple: do various things to ensure I get a good night's sleep (which for me is 7.5 hours without waking up) and take a 20-minute nap in the afternoons. If I do these two things, my mind feels stronger for longer, more often at its best. If I don't, it can feel weak and drained and distracted.
I have also found eating less sugary foods tends to help, as does exercise, though I can't see as direct a impact on brain energy as sleeping and napping.
I suspect there's a lot more I could do. The brain consumes a great deal of a person's energy, perhaps even more dramatically for folks like me (and I suspect many on HN) whose minds are always buzzing with thought all day long, and I'd like to find more ways to "feed" it on a day to day basis.
So I ask you fellow hackers: what sleep, food, exercise, or other habits have you found to be most effective in fueling your day-to-day brain power?
This Dr Terry Wahls TEDx talk has been very motivating.
Minding Your Mitochondria http://www.youtube.com/watch?v=KLjgBLwH3Wc
Dr. Wahls is mitigating her MS thru nutrition. For me, eating lots of vegetables makes my chronic psoriasis go away. When I slack on the nutrition (eg traveling), my psoriasis comes back.
I believe, but cannot prove, that psoriasis is basically external arthritis. I figure better nutrition is improving my health overall, including brain function.
One side effect I did not expect: I now crave hearty kale salads. Years ago I had a gf who was really gunghu for kale, chard, sorrel, and other leafy greens. I could handle it once or at most twice a week. Blech.
Now things are different. Better recipes certainly help. I think once my body got used to the good stuff, it demands more.
Moderate exercise and plenty of sleep too, of course.
Good luck.