Abraham Lincoln was no stranger to dealing with difficult people. He frequently encountered individuals who would fan the flames of Presidential irritation, causing Lincoln to want to tell the offenders exactly what he thought of them.
On such occasions the President would sit down and compose something he called a “hot letter.” Holding nothing back, he would put all of his angry responses on paper, leaving no doubt as to what he thought about the person in question.
Having given voice to his anger, Lincoln then set it aside for a while, waiting to cool down. Once his temper subsided, he’d write, “Never sent. Never signed” on the letter and set it in the fireplace, watching his fiery words and passions be consumed by the flames.
For another example of a President following this practice, look here.