I'm reminded of a biography of Harry Truman (
the one by David McCullough) I read a number of years ago. Truman wrote lots of letters to all kinds of people. Apparently, he hand wrote 1st drafts of these letters, where he really let loose with all kinds criticism, harsh comments, and Major League cursing. He would put these away in a desk drawer for a day or two, and then write a 2nd draft where he cleaned it all up.
He kept all those 1st drafts, even if he never sent any letter at all. Historians loved it when they got their hands on those 1st drafts, as they could compare it to the official revised versions that did get sent. It really helped biographers like McCullough understand what he really thought. But it also revealed his thought processes as he revised those letters. Truman even said that he was often embarrassed by what he said in his 1st drafts – but only after a day or two had passed.