One of the reasons I like reading old letters and diaries is that people censor themselves less than if they were writing to an audience. They are not trying to sound impressive or worrying whether their thoughts are interesting, but rather writing clear and hard about what they want to say. Using plain language to put their mind, as it is, on the page. In a strange way, this often makes for good writing. The lack of rhythm becomes its own kind of rhythm, the casualness creating a sense of comfort.