My daughter is my first-born, and as with all mothers of firstborns, I didn't know any differently. I knew she was a hard baby, that was evident-- she was the type of baby to make a fool out of sleep training, a baby who learned to fake cough at 12 weeks for attention-- but I had no idea what I was up against until her emergence into toddlerhood coincided with the birth of my easygoing son. Not only did it strike me that not all babies are that exhausting, but I also came to understand what it meant to have not just a toddler, not just a hard toddler, but to be the parent of a strong-willed child.