I think I know the transition you are referring to, LG, as I feel like I've had it half-flipped a couple of times over the years before finally flipping it all the way.
It was a process of elimination: after eliminating everything else in my life (family, friends, former colleagues, vacations, hobbies) besides work and palliative booze--there wasn't anything left to blame for my downward spiral. One day after running into a random acquaintance on the street that I didn't want to run into (and having THAT "what are you up to?" conversation), I just felt ashamed of my life, ashamed that I couldn't function normally and felt I had to hide from everyone, and also suddenly aware that things were going to get a lot worse for a long time if I didn't find some way to get more comfortable with life. I just thought to myself, well sh**, you're not such an idiot that you can't figure this one out. Obviously we need to stop drinking entirely and start normalizing.