DRINK. If you smoke or drink, keep right on in your regular habits, don’t change them; no training pays except practice. If you drink as you shoot use ale, beer or light wine. DON’T drink whiskey or strong liquors, they slow the eyesight, and while you appear to be holding and pulling cleanly, you do not get your shots because you do not see as well as you think you do. Don’t drink a swallow or two at a time as a glass will chill the stomach every time, and the nerves are then unsettled and you cannot hold steady till you get warmed again. –from IMPORTANT THINGS TO REMEMBER IN OFFHAND RIFLE SHOOTING, GALLERY SHOOTING ESPECIALLY by H. M. POPE
you can read some of Pope’s other “things to remember” in South-Shore-Rifle-and-Pistol-League-50-Years (PDF, 34MB)
This presumes that one is not preparing for three gun competition. In that case, perhaps beer, wine and whisky (note the “e” omitted with prejudice!)might be an appropriate training regimine. I will leave it to the audience to determine which is best suited to the various shooting disciplines…
and while the old adage to avoid the mixture of grape and grains might have some inherent wisdom, it can help tremendously in soothing the memories of cross-fires, snowbirds and other shooting maladies!