Memoir authors are typically told they should center their story around one particular theme or time period. In response, they tend to write about subjects like divorce, abuse, health struggles, caregiving, or travel, all of which have been extensively written about already. Other writers ignore the advice and try to pack their whole life into a single narrative, sometimes shoehorning two or three unrelated books into one. As a book editor and writing coach, I’m sometimes asked if I agree with this advice …