As an experiment, I’ve reduced my coffee-intake to a single cup a day for about a week now. It’s made an enormous difference in sleep, mood and energy. I get tired at night, fall asleep quickly, and wake up refreshed. As mentioned previously in the context of morning sunlight exposure—another thing that’s aided my sleeping habits, but is somewhat less practical to sustain as it requires fair weather—I’ve always been slow to get going in the morning, active at night, bad at getting to bed at sane hours. Tired when I should be awake, and awake when I should be tired.