Step One can get complicated when you look at it from the inside.
Let's try looking at it from the outside:
If a person drinks with bad consequences a few hundred or thousand times over the course of years, why?
Consequences clearly don't trigger moderation. Something is impelling the person, when they drink, to drink too much. We say it's the 'physical craving' (see The Doctor's Opinion). But even if they're doing it because they're thick, mad, or otherwise soft in the head, the result is the same: moderation ain't never gonna happen.
If that be the case, to have the first drink is insane.
If they do, they're insane.
Broken body, broken mind, case closed.
What the individual thinks is going on is irrelevant. All you need to look at is what happens.