The biggest factor for me was that deep, deep down, I simply didn't want to quit. I told myself I did and then that decision would flip 180 degrees in the blink of an eye. I could moderate! I deserved a drink! I was tired! I was stressed! Bored, lonely, anxious, happy, sad, blah blah blah. Each and every one an excuse to tie one on.
It all stemmed from a deep unwillingness to sit with whatever emotion was there and simple experience it and then move on.