The importance of coffee in this equation cannot be overstated. If you’re worried, try having a 12oz coffee plus lots of water an hour or two before your appointment. Don’t hold it in all day before the appt, you might hurt yourself. Just goose your waterworks with coffee and stay well hydrated before going in and you should be fine.
Also, doctors know about bashful bladders so just let them know you might be a minute. You may also be able to collect a sample at home if you discuss it with them first(don’t roll up to your doctor today with a cup of unasked-for pee). You’ve got options. Just when you’re in the moment, relax and let the coffee do the work.
I had a friend tell me a few days ago that they get up an hour and a half before they’re supposed to work to relax and read or shower or whatever. I can’t even picture that. I get up 30m before work and rush through coffee+oatmeal because if I slow down and think about how I have to work today it’ll make me depressed.
It’s better to catch me unawares so I don’t have time to ruminate before I’m expected to work. Then before I know it I’ll be working and too busy to think about how I’d rather be floating on a cloud while beautiful people feed me grapes off the vine.