Little kids read a monster book and then hide under the bed, right?
Well, sometimes the monsters follow you the rest of your life...or you acquire new ones as an adult. What irrational (or quite rational) worries have you acquired as a result of reading? Have any of them ever kept you from making mistakes?
Tiny Little Medical Problems: I've been paranoid of splinters ever since reading On Tide Mill Lane. Wouldn't you be?
Bad salmon: Flight into Danger, required reading in grade five or six.
Bad whipped cream: A Cap for Mary Ellis.
Leaving things too close to light bulbs: The Saturdays.
Creepy old houses, not to mention reading under the covers: The Letter, the Witch, and the Ring. You wouldn't believe how badly that book scared me one night...it cured me of after-hours reading for some time.
Running with scissors: The title, I can't remember; but it was a Parents' Magazine Press book from about 1970, about safety rules. A bit like Struwwelpeter although not so extreme. One little raccoon "liked to cut paper dolls, she snipped away happily singing" until she heard a friend's bicycle bell ringing--and ran with scissors, to what end exactly we're not sure. [Oh, look at that: I just found the title. Watch Out! How to Be Safe and Not Sorry, by Harold Longman.]
Teasing Weasels: if the opportunity ever came up.