I once thought it was not worth sitting down for a time as short as that; now I know differently and, if I have ten minutes, I use them, even if they bring only two lines, and it keeps the book alive.
I'm writing a book on Performance-Based Project Management. This quote has guided me in my efforts. Short, quick, directed edits to emerging ideas, one chapter at a time. Then off to the editor, back with markups, then a dedicated review of the content, themes, and narrative flow.