There have been times in my life when I’ve had coffee every day, times when I have been been caffeine-free, and times when I have limited my caffeine intake to 20 mg or so (around half a cup of tea). I am intentionally very wary of my consumption of drugs, so I have paid a fair amount of attention to how my mental & emotional states are affected by this usage.
It almost goes without saying that people respond very differently to caffeine. My experience will not generalize to yours, but it could still be somewhat informative. Also it’s helpful for me to write it down and get all my thoughts in order about it.
The first time I have a medium dose (> 50 mg, or about half a cup of coffee) after not having it for a couple days, I feel a surge of productivity and focus. I am able to concentrate for much longer than I would otherwise without it. My mood is higher; I feel better about the world at large and my place in it. I can exercise more easily. It’s a good time.
If I have a large dose (> 120 mg, or about a whole cup of coffee), I feel very “wired”: jittery, anxious, finding it hard to focus on anything. Sometimes it works out okay, sometimes it is just not fun.
I can work my way up to a large dose over the course of several days, but I find that whenever I take medium or large doses of caffeine every day for about a week, I lose the beneficial effects. I become anxious, irritable, and actually less focused.
I try not to have any caffeine after 11am or so. I think its half-life in my body is around 8-9 hours — on the upper end of normal.
I’ve landed on using caffeine sparingly and intermittently. Consuming small amounts of tea frequently, with half a cup of coffee thrown in every now and then, seems to suit me very well. I might experiment alternating between half-a-cup and zero-caffeine days in the future.
That’s all!