“How do you quit a job?” Nobody asks such a question because the answer is incredibly simple. You tell your boss “I quit,” and then you don’t return there to work. The real issue is whether you want to quit that job or keep working there. Do you see a better alternative? Do you think it’s worth leaving that job? Do you think you’ll be happier if you do? The answers to such questions determine whether you’ll want to quit, and then the actual nuts and bolts of quitting are simple; you just say “I quit” and then go on your merry way. You don’t need to resist going back to that job every day.
“How do I quit drinking?” is the same sort of question. It is fully a matter of figuring out what you want. When you know what that is, you just do it. It doesn’t take any strength or willpower to not do what you know you don’t want to do. It doesn’t take any special techniques or steps. There’s no effort needed to maintain not drinking or drugging (or moderating those activities), just as there is no effort needed to not work at the job you quit. The effort is simply in figuring out what you really want and then naturally moving in that new direction.