There is certainly a downside of caffeine, which is stopping. It is hard to remember times in my life where I was not drinking four or more caffeinated beverages a day. What I do remember is most of the times that I stopped with caffeine.
There are two possible reactions to stopping caffeine for me. The first is nothing happens and life presses on. This is by far the best scenario. It usually happens when you are unaware you are giving up caffeine or have the decency to slow down, rather than hit the breaks and stop cold turkey. You tend not to have caffeine at 11 PM and say, what a fine choice this is. Instead, you go from 4 to 3 to 2 to 1, in a nice, safe decline. You eventually start back, either unthinkingly at a restaurant or knowingly, because something just has to be done and back on the horse you are, blissfully unaware your detoxification failed.
The other possible reaction is the dead stop. Rather than go to the store the last few days, I said, maybe I'll just give up caffeine again. A sound plan, except for the part where I was up until 4 AM on Monday night, restless. So, Tuesday, caffeinated beverages gone, six inches of snow on the ground, I go about my business, I was a little tired by the end of the night, but thought nothing of it.
And then tomorrow comes. I wake up early, but with nothing specific to be handled, I take myself from the couch to my bed and decided to sleep some more. Barely awakening to a confirm and take a phone call, I set about my day. I take a second phone call, get ready to take care of a few errands and the wall comes crashing down. I was ready to leave, but my mind checked out and said, "NAP TIME!!!" I actually dropped my computer out of my hand at an awkward angle, which led to the power cord reaching its end time, requiring me to either find the spare or make this one last until early next week.
At which point I dragged myself back to bed, woke up three hours later with a splitting headache and the sensation I should not have given up caffeine and this very unilluminating blog post.