A few months before my 42nd birthday, I was out to dinner with friends and found myself seated next to a well-known older male writer. I happened to be in the final stages of finishing a proposal for a memoir about being a single woman over 40 without children, and was inwardly marveling at the timing of our encounter. I was a fan of his. Perhaps he might offer some wisdom? Words of encouragement? As drinks were delivered I sketched the outline of the story: No one had prepared me for how exhilarating life could be on my own. I...