Couldn't agree more with you Tightslot - no matter how rubbish a day I've had, or how long the delay has been, I will ALWAYS make eye contact, smile and say hello to whoever is greeting me at the door. Apart from anything else, it makes ME feel better as a humble SLF - gets me in the right mood for the flight, moving on mentally from any issues before boarding.
As has been said in many places before, wx, tech, inbound delays, air traffic etc are not within the power of the CC to change. I guess there will always be those who just don't understand that you are not (completely) all knowing and powerful.....