I'm lucky I guess that this isn't an issue for me - I don't drink and haven't for many years (just don't like the taste and as it's a social thing and I never socialise....), and my use of drugs ceased when my irresponsible youth slipped away back in the Jurassic. Also I have two sets of ageing relatives living very near, and I never know when someone will need driving to the hospital or doctor. I would feel terrible if I had to refuse due to having had a drink or two.