I read with interest a lot of people's advice on here about planning their finances. Some even have budgets down to the last penny.
My question is pretty simple - if you're of that mindset - what do you do in situations when something comes up that's not part of your "plan" in a social context? As an example let's say you've done your monthly budget and you randomly get invited to a party/event. There's a bar and you're with friends who say "let's go out for a few more drinks/whatever" (e.g. after work). If the event was unplanned/unforseen in advance, you cannot have accounted for this. Do people of the budgetting mindset allocate some spare funds for this type of thing, or do they simply say "no it's not within my budget"? Or do they make up the difference another month? I'm interested to know what people do in this situation as it seems to not fit in at all with some of the advice given on this site, but is a very common scenario where I live (UK).
I'm interested in advice from a social perspective - how can you work around this situation whilst not seeming anti-social or not wanting to socialise with your friends in events that you get drawn into without much prior knowledge?
Edit - going for a drink is just an example. The question is not limited to this but literally any types of social event (e.g. cinema, dining, trip out, etc) that one may be invited to.