For me, reading baby sleep books frightened me into thinking my baby had to learn to self settle. 'They say' inability to self settle is the cause of all other sleep problems: catnapping during the day, frequent night wakings, etc. You can assist a newborn, or a one, two or three month old, but older babies will start waking after an hour or two of sleep if they are unable to self settle. The books make you believe that your baby's sleep issues are a direct result of how you parent them to sleep, scare you into sleep training with the prospect of years of sleepless nights, and for nervous new mums like me, want you to believe that there's a one size fits all approach to all babies - if you can make your bub fit the textbook, then you're doing it right.
Took me a long time to accept DS wasn't a textbook! Though I'm still not sure his catnapping isn't my fault... Sigh.