Buffering question

I have developed a drink plan which has me not drinking at all except for when I go out with girlfriends. In those situations I allow myself one drink. Typically I’m able to plan these 24 hours in advance. My question is about spontaneous gatherings. If we make plans to get together at a time less than 24 hours in advance, is it OK to give myself a “floating pass” to have one drink on those occasions?