Some athletes, even elite ones, find that 1/3 or 1/2 serving of alcohol prioe to competition can promote relaxation to elicit a peak performance. Any more than that and reflexes/reaction time will be impaired.
I will usually drink 1/2 to one serving of red wine (or occasionally beer) a day. Note, however, as ollinger
indicates, even moderate drinking can result in an increased risk of dementia.