I have known a lot of people who use drugs but, I don't know of anyone who can use cocaine or heroin just occasionally. As for being able to occasionally party that is a lie they tell themselves to get started again.
yes yes yes. this is stinking thinking and I'd be very wary of believing that anyone who has this kind of thinking will stay clean for very long.
that's why addicts who recover stay in the moment and live "one day at a time". We don't have to feel worried that we need to stay clean for the rest of our lives. We only have to stay clean right now. And everything else will work itself out.