I generally make it a hard and fast rule never to drink before diving, and to restrict my drinking the night before I plan to dive. Since I like alcohol (in moderation), this is not a teetoller's response. Since I dive frequently, my average intake of alcohol is limited to a few drinks a week.
I am an older diver who usually dives solo. I do not want my mind (or body) clouded by alcohol on my dives... whether from the night before or the day of.
I remember one incident in which I dove after partying most of the night with my DM in Thailand. She was an absolutely beautiful (inside and out) diver from Holland and I could have fallen deeply in love. I let that cloud my judgment, dove the next morning after far too much alcohol and far too little sleep. Although the dives were uneventful, I feel it was a major mistake. My life is worth far more than a night of drinking and dancing even with such a wonderful woman!
Dr. Bill