Many people are too self-centered when they write.
That slows me to a crawl, and my first draft of even one brief chapter could take days. Bonus: Author William Shunn has prepared an excellent guide to formatting short stories, which you can download at no charge. Go for a walk. But there are some ways that are easier, faster, and more successful than others.
Letters allow us to be blunt without having to face the music right away. If you use the correct font, one in which each letter takes up the same amount of space, it becomes very easy for the publisher to know how many pages the final book will need.
And you might be wondering, which topic should I write about first? Review what you wrote yesterday to refresh your memory. Spanish foreign minister Juan Valera's Pepita Jimenez is written in three sections, the first and third being a series of letters, the middle part narrated by an unknown observer.
In the second piece, a character explains that he is writing his portion because another had observed to him that the events surrounding the disappearance of the eponymous diamond might reflect poorly on the family, if misunderstood, and therefore he was collecting the true story.
Some like to write their entire first draft before attacking the revision. Then I switch hats, tell Perfectionist Me to take the rest of the day off, and I start producing rough pages again.
And speaking of chaos: let thoughts wander — to an extent.
Most who fail at writing a book tell me they give up somewhere in what I like to call The Marathon of the Middle.