Back in the days when I was a Good Mommy, I tried to do everything right. I breast-fed and co-slept, and responded to each and every cry with anxious alacrity. I awoke with my daughter at 6:30 AM and, eschewing TV, curled up on the couch with a stack of books that I could recite in my sleep. I did this, in fact, many times, jerking myself back awake as the clock rounded 6:45 and the words of Curious George started to merge with my dreams. Was I crazy? No—I was a committed mother, eager to do right by my...