Never never never say Oh **** when a passenger can hear you.
I've thought of that one, which is why I include that as part of the passenger briefing.
"Don't worry if I start talking to myself, many pilots do it. It's a habit we get into explaining to instructors and examiners what we're doing, and many of us don't get out of it.
"Further, don't worry if I start swearing to myself. Usually this simply means that I'm displeased with myself for having done something slightly less neatly than should have been possible; it will almost certainly not be an indication of a real problem."