I had a related phenomenon....
I would use my exercise as a justification.
Yeah... I can totally cut loose and get blasted... .hell I've been working out HARD!! No problem.
What a stupid line of thinking!!
And it sure caught up to me. I'm still slogging my way back to the shape I was once in (when I was sober for almost 6 months and in just incredible shape).
The "why"? Sounds like maybe because you're an alcoholic.
It's not the exercise, I gurantee you that.