“Be professional, be polite, but have a plan to kill everyone you meet.”
“... have a smile for everyone you meet and a plan to kill them.”
“Be nice to everyone you meet...but always have a plan to kill them.”
“Have a smile on your face for everyone you meet, and a plan to kill them.”
“When you have to kill a man it costs nothing to be polite.”
“Be genuinely interested in everyone you meet and everyone you meet will be genuinely interested in you”