Not sending a letter written in anger  Lincoln’s advice to a politician

Lincoln’s secretary of war, Edwin Stanton, had some trouble with a major general who accused him in abusive language of favouritism.  Stanton complained to Lincoln, who suggested that he write the officer a sharp letter.  Stanton did so, and showed the strongly-worded memorandum to the president, who praised its powerful language. «What are you going to do with it?» asked Lincoln. 
Surprised at the question, Stanton said, «Why, send it, of course.»
This historical anecdote continues…

«You don’t want to send that letter,» said the President.  «Put it, in the stove. That’s what I do when I have written a letter while I am angry. It’s a good letter and you had a good time writing it, and now you feel better.  Now, burn it and write another one.»