Health - it took a mild attack of pancreatitis to get me moving. Even then I drank another 3 months before a weird first-date thing happened and I finally questioned my future and took action. Plus triglyceride levels over 700 and blood pressure sitting around 140/110.
At 45 years old with those issues I was clearly getting into the territory where I was facing my own impending mortality if I kept drinking. I'm lucky the things that caught up to me weren't permanently disabling or fatal.