Incognito,
In answer to your question I guess for me I saw my bottom coming at me like a buldozer and just knew if I didn't do something, I was going to get sicker, my excuses would get worse, I'd live in denial all my life and my family and hubby would have to throw in the towel and let me be as there wasn't anything they could say to help me quit.
I knew I was bad off, and saw how easy it would be for me to get much worse, lose my job, endless hangovers, the just screw it attitude, and for me the lonliness and self hatred was stifling!
I maintained my job without passion, managed my household like a rightious bitch, and made any excuse to drink, and any excuse to be hungover. It was enevitable I'd loose my job, my hubby and kids, my self respect, not to mention my life.. I saw it coming clear as day.
So I am grateful I found the strength and willingness before I hit my bottom, to get off the rollercoaster and seek out the person I used to be, happy confident, loving and passionate about life. I see her just down the road, because my family here and in the rooms have shown me the way.