I sometimes thought about a letter for a week before writing anything. It's something that you must do even if you do not have the leisure of being in prison. To write, you must work methodically, forming your thoughts and prompting other people to think as they read.
Writing requires work at both ends.
That's what makes it special. Writing is easy. All you do is stare at a blank sheet of paper until drops of blood form on your forehead. This happens every time. Then gradually I write one page and then another.