One of the great “be careful what you wish for” stories is The Monkey’s Paw in which a family receives a magic item that grants wishes but discovers to their horror that all the wishes are granted in terrible, horrible ways. I can’t remember when I last read the story (though I’m confident I have—maybe in high school?), but monkey paw has stuck in my brain as the metaphor for this idea that wishes can go terribly, terribly wrong, so you really ought to think them through.