Me. A couple years ago a guy I worked with started mixing decaf into my coffee (We brewed it at work, and he was always there before me, so he brewed the coffee), because he thought caffeine was making me angry (It wasn't the caffeine, it was our psycho asshole co-worker).
One day he said "how do you like decaf coffee? You've been drinking it for 6 months now". I was pissed. Now caffeine makes me feel like I'm gonna die. I can't drink it at all anymore. My heart races and i cant breathe, my head weighs 100 pounds and I get dizzy... it sucks. I miss coffee.
I still drink decaf every day, out of habit, but it takes me 3 hours now before my head's together and I can be productive.