I love coffee but I feel three per day is pushing it. Do people really drink much more than that?
All these personal anecdotes (when I stopped drinking coffee, my wife returned to me, and I won in Powerball!) sound very strange to me.
Anyway, I'm like you, and actually once said "I have no caffeine sensitivity LIKE AT ALL", and then I cut down from "last coffee before dawn" to "around 1.5L" and the amount of psychological side effects I stopped having did change my life (no Powerball involved). At the time, of course, I would have called such side effects "that's just me". So, mileage varying. And some people are super sensitive to that somewhat racing adrenaline feeling, even though it is not actually dangerous.
Not a conscious effort... Just sorta happens.
For me, it was something I could sip all day long, especially as black coffee is a tasty zero-calorie beverage, and at least in the morning I'd feel that rush of focus. Eventually had to give it up due to insomnia.
But I've worked with people where effectively there wasn't a moment in the day they weren't drinking coffee and they were going to get more pretty much constantly.
I didn't realize how much people drink until I started.
I find I just like to sip on something constantly, and water gives me a headache.
I'd see a doctor about that, water shouldn't give you a headache unless you drink much more than 6-8 cans worth a day, you might have a sodium deficiency or have something else wrong. Maybe even a sugar come down from the 6-8 cans of soda which is far from healthy.