About six years ago, I woke up one morning, realized that I didn't have any cigarettes left, and decided that it was easier to quit than to go buy more, so I did. It was remarkably easy.
About a month or so ago, I decided that caffeine wasn't having any positive effect on me, and all I was doing was fighting off withdrawals, so in the interests of removing my caffeine tolerance so that it could be useful to me in future, I decided to stop drinking it, and I did (with a one-week "OH MY GOD NOT THE HEADACHES" weening period of one can a day).
However, what they tell you about these things is rubbish. Quitting smoking didn't make me feel healthier and more spritely and give me my sense of smell back - it just made me feel like eating all the time. Quitting caffeine didn't make me feel vigorous and calm - I now just sleep for nine and a half hours a night.
This public service announcement bought to you by the man who took fifteen years to see a correlation between eating spicy food and getting stomach cramps six hours later. So you should probably ignore it.