How to win friends and influence people

is a great book by Dale Carnegie. As usual I'm going to quote from a few pages:

Any fool can criticise, condemn, and complain - and most fools do.

Action seems to follow feeling, but really action and feeling go together; and by regulating the action, which is under more direct control of the will, we can indirectly regulate the feeling, which is not. (quoting William James)

Good manners, said Emerson, are made up of petty sacrifices.

I made it a rule, said [Benjamin] Franklin, to forbear all direct contradiction of the sentiment of others, and all positive assertion of my own.

I judge people by their own principles, not by my own. (quoting Martin Luther King)

Any fool can try to defend his or her mistakes - and most fools do.

If there is any one secret of success, said Henry Ford, it lies in the ability to get the other person's point of view and see things from that person's angle as well as from your own.