I'm sure that I've slipped and not been as nice as I should to someone, but I do try.
Recently, I saw someone be devastated by another person who I don't think even realized the effect the words spoken had on the other person. Most of the people around didn't realize it either.
No appreciation was shown for a big job well done, but plenty of criticism was heaped upon the person.
Frankly, if it had been me I'd have let it roll off my back. If I know I've done a good job that's all I need. Some people just enjoy picking at others--though if it happened to them, I'm sure they'd fight back.
Being critiqued is fine--but anyone who is doing it should also point out the good. This goes for critiquing someone's writing as well as a job that's been done.
A smile goes a long way too. I make it a habit to smile at strangers and I almost always get a big smile in return.
I guess my message it this would be a much happier place if we smiled more and tried hard to be nice to people.