I'm not sure that it was strength or willpower that got me to quit. I'd say it was sadness over the mess I was making of my life and my child's life. It was disgust at how awful I looked and felt. It was, as others have said, acceptance that I had a problem and sobriety was the only solution.
Day by day, I remind myself that if I just put one foot in front of the other and do*whatever it takes* to stay sober, I can do it. And I remind myself of how awful I felt after drinking and how much I don't want to go back to that.
It gets easier with time, though there are still difficult moments and difficult days. I'm only at 2 1/2 months, so I'm still working this all out. But I've accepted that this is my only choice if I want to have a happy and healthy life. And I really do want a happy and healthy life. Sounds like you do too, enough.
Delfin