I think most of us recognize that sense of being on auto-pilot and the feeling of simply not being in control. I have often thought about this and am genuinely baffled by the influence our addictions can have over us.
Maybe think about keeping more distance from alcohol for a while? The walk over the cooler wasn't necessarily going to be long enough to check yourself fully. Addicts are impulsive and need to protect themselves from making mistakes. If you had to get in the car, drive to the store, drive back etc. then there would be more time to analyze where the urge was coming from and stop yourself. Just making it a bit more difficult might have helped.
If you were doing well, you can do well again! You don't have to feel like this again!