Etiquette rules have been in existence since the beginning of socialization. Abraham Lincoln spoke wisely and often about behaving and acting with good manners. Here are some of the things he said.
On conversation:
”Better to remain silent and be thought a fool than to speak out and remove all doubt.”
On giving credit and acknowledging others:
”All that I am, or hope to be, I owe to my angel mother.”

”Books serve to show a man that those original thoughts of his aren't very new at all.”

On holding true to good behavior:
”Be sure you put your feet in the right place, then stand firm.”
On being responsible for your own actions:
”You cannot escape the responsibility of tomorrow by evading it today.”
It is what it is. Bad manners are bad manners, even when you call them something else:
”How many legs does a dog have if you call the tail a leg? Four. Calling a tail a leg doesn't make it a leg.”

“Important principles may, and must, be inflexible.”
Do the right thing, even when you think others aren’t looking:
”Don't worry when you are not recognized, but strive to be worthy of recognition.”
Learn from your mistakes:
”I do not think much of a man who is not wiser today than he was yesterday.”
On gossip and misguided judgment:
”I have always found that mercy bears richer fruits than strict justice.”