Then I fall asleep. Often the last thing that happens in my day is a headache. On days when I don't do caffeine, I don't do anything else either. I lie there and vegetate. Even that is exhausting.
Caffeine gives some people jitters.
That doesn't happen to me, though sometimes I do get indigestion. When I do, I take a little baking soda in water and it goes away instantly. Aspirin cures the headache just fine. If they are right, the amount I do is definitely bad for my health. If they are wrong, it's not.