The only thing I can say is be supportive no matter how small the situation is causing anxiety. Even if you think it’s ridiculous try and understand it from their point Explain all the positive things about it. This will take their mind away from thinking about all the things that can go wrong in this situation. Some days the same situation may cause a worse/less anxiety attack. I always find that it’s worse when tired so try and get a good nights sleep if you’re doing something the next day you are worrying about.