That is only caffeine, of course. But even heroin users can addict themselves and then quit as circumstances dictate. Psychiatrist Lee Robins found that almost half of American soldiers used heroin or opium while in Vietnam, but rather fewer were actually addicted, and almost 90 percent of those kicked the habit upon returning to the United States. I have absolutely no desire to try heroin myself, but it seems that both the decision to start and the decision to try to quit were, like my coffee habit, rational responses to circumstances.
I can't help noting that a large number of British cabinet ministers decided to smoke marijuana at college and then quit later. Whisper it softly, but perhaps not only addicts are rational, but politicians, too.