Pete,

I'm a relative newb, but I think that "game face" is common and healthy. I make my dumbest mistakes when I am most relaxed and yucking it up before a flight. And especially when I am fueling or preparing to start, I don't want any distractions.

I understand when non-jet guys don't get this because their machines are so much simpler, so I politely tell them I don't want to be rude, but that I'm gonna concentrate on my task at hand so I don't goof it up.