I have anxiety. At times it can feel crippling. Having someone tell me to calm down is like pouring gasoline on a fire: it does no good- and actually makes it worse. If 'calming down' was that easy don't you think I'd do it?? Would you tell someone having a heart attack to just stop? No? (I certainly hope not, at least.) Then don't tell me to calm down.
Its insulting to be told that- as if I had some choice in the matter. Anxiety is not something that I can schedule. It just is.
Another thing not to do-- for the love of all that is holy- do not try and surprise or scar me. I may surprise you by hitting you.