{{omnis}}
See also: Parents who think they get to take credit for their babies' good sleep habits. If your 9-month-old sleeps through the night, I envy you. I really, really do. But the fact that mine doesn't is really not evidence of parental incompetence on my part. Some babies just don't sleep.
My mother still reminds me that my sister was a perfect baby who slept through the night at five months, and I didn't sleep through the night until kindergarten. (By the time I was a toddler, I'd pretty much learned that waking up my parents in the middle of the night just because I was awake wasn't such a good idea, so I'd play with my dolls or read a book or something until I felt tired enough to go back to sleep.)