To quote Denis Leary, "It's a drug, I'm Addicted, OKAY!" Once you start with caffeine, it is so prevalent in modern food and drink, that even when you are trying to quit the addiction you are still feeding it.
As a child we used to have an electric fence, and I would occasionally hold on to it until a pulse of electricity came through. It would give me a little shock and jolt, but it was one hell of a rush. And it hurt a little afterwards, well My arm was sore. Yet that never stopped me from doing it because of the little rush.