I sometimes go without things, just to prove to myself that I can, and to see how dependent on it I am.
For example, I went without drugs for about a month a while ago- no dope, no alcohol, no caffeine. Alcohol was a little tricky, just because of old habits. I once or twice forgot I wasn't allowing myself drugs, and just about had a glass of wine or something. No danger of forgetting I wasn't having caffeine; that was frightful. I am addicted to coffee, that's for sure.
Since getting a high speed connection, I haven't tested myself on that addiction for any meaningful period...