I agree that the 'why' is not nearly as important as is putting down the drink. For this, I'll again reference the Parable Of The Poison Arrow.
As long as we continue to fail, we have a built-in rationalization to continue drinking. It's what we do.
In the AA Big Book, there's a line that goes something like, "Alcoholics have a knack for going on a bender at the most inopportune times." Doesn't sound like you went on a bender, but you drank enough to get the same results.