I stopped drinking caffeinated beverages for the most part last month, and it was a tough week with a lot of headaches. If you can go more gradually, it'd probably help.

Now it just stinks if I go out to eat or something because I have to choose between a diet soda with caffeine, a high-calorie soda without caffeine or water (which I drink a ton of already so gets boring). And of course the Gu I already own has caffeine in it.