I'm reminded of this video, Jill - if you haven't seen it (hard to imagine that anyone HASN'T!), I think you'll enjoy it.

https://www.youtube.com/watch?v=nwAYpLVyeFU

I don't think "up all day" is an excuse, but I do think that hostile people are generally people who have not had much kindness or thoughtfulness shown to them in the first place. I've felt myself getting sucked into that place (it usually happens when we've dealt with the third or fourth incompetent "customer service" person after spending a night in the airport with two small children kind of thing). Unfortunately, it's that last person who tends to get the brunt of it. They deserve their share, but not the ire generated by the 10 who came before them. That's when we need to watch that video again. Maybe on repeat. ;)