When trying to overcome an addiction, I've read that you should think of every failed attempt as "practice." I've been practicing quitting caffeine for a long time now. Because I love my Coca Cola so much, my past attempts have revolved around decreasing my consumption. Those attempts have all been miserable failures. My five-can-a-day habit would reassert itself within a few days.
For some reason, this week I have an exciting new level of resolve. Tuesday night I was driving home from the barn, really craving a Coke. I realized I didn't have any at home. And I suddenly said, that's it! I'm quitting! I am not dragging myself to the grocery store with this giant greenish-brown horse kiss all over the front of my white shirt! (My grandfather told me a similar story about quitting smoking: he was way the heck out in the middle of the north forty combining, and he realized he really needed a cigarette, his pack was empty, and his pickup was very far away. He got mad and quit.)
So I'm 48 hours into the cold turkey experience. I had a miserable headache last night, although I found that working up a sweat riding seemed to help it quite a bit. I suppose the trick is to keep your circulation pumping. Today I just feel foggy and tired, but the headache is mostly gone. I'm using Gatorade as my crutch. I was hit with a severe Coke craving around lunchtime, but I just kept sipping the Gatorade and it passed.
Wikipedia tells me the first 48-72 hours are the worst, and all withdrawal symptoms should pass after a week. Wikipedia also provided this helpful illustration to keep me motivated: