My personal "calm down and focus" phrase is from The Hitchhiker's Guide to the Galaxy. It is:

Don't Panic

It helps if you imagine it in big, friendly letters, as it appears on the back of the Guide, itself.

Point being, you can make anything a "loaded" phrase that can work to just get you focussed and help you avoid losing your balance (that's always what it feels like to me, by the way; I sometimes describe it as "falling off my perch"). I like that one because it's funny and a little silly and has positive associations for me, but, really, whatever you like and intend can and will work.

I didn't think I had much more to say on this topic, but I guess I did.