Some interesting replies.
Maybe I should have prefaced my original question. I'm always in condition "yellow" and have walked out of many places because there was somebody there who was acting funny, belligerent or just seemed a little off.
I also agree that there are no "safe" places since there are evil, crazy, dangerous people everywhere. That said, I fully intend to live my life and enjoy it as I see fit.
To a much greater extent than most mechanical devices, firearms are terribly unforgiving of any overconfidence, complacency or negligence.