A surprising thing about some of us people who deal with anxiety over years is that we may appear unusually calm, cheery and laid-back to others. Sometimes we actually ARE calm, especially when everyone else is in a state of alarm - something is on fire? Tigers attack? That's just how we sometimes feel because it's Wednesday and we are alive. No big deal.
Sometimes, however, we actually are smiling through an anxiety attack.
After all, we are very used to them and would prefer if you did not make a fuss.
Making a fuss makes the situation worse.
So if the anxious person in your life seems to just be smiling at the void and replies to every suggestion with "I am just fine", "if you like" and "I don't mind" they are probably dealing with an attack. - Don't mention it. Don't try to snap them out. Don't worry. Offer them a cup of tea, and go about business as usual. They'll tune back into the real world eventually.
We don't do this to make people worry about us. We are not lying to you or shutting you out. You really can't do anything to help, and you don't need to, neither. Just let us sit and smile a while. In a way, we actually are calm and happy, because we are dealing with things in the best way we have learned. - It's not poignant, deeply meaningful or weird. It's like holding in a sneeze. It's normal.