Per my original comment - that was because each time my spouse started smoking again, and was pushing cigarettes on me. If I hadn't been married to them, then I would have stayed quit the very first time I stopped. Each time we quit smoking, they would secretly start smoking again almost immediately, and would then start pushing me to re-start after a couple of months. Once the divorce was in progress and we had limited contact, it was fairly straightforward.

It would probably be super hard to quit heroin if you were married to your dealer.