The version that is more familiar to me is "be careful what you wish for, lest it come true", which always makes me think of the Tale of the Monkey's Paw (Edgar Allen Poe?). Fortunately, when right-minded and well-balanced people come together in communal accord and consensus, the extremes warned about by Mr. Poe (if it was he) never occur.
http://www.phrases.org.uk/bulletin_board/37/me ssages/1134.html
When I was a little girl, I had desires like you
One of everything, all the riches
How could I help myself?
I was so na�ve, Santa Claus, Christmas eve, ohhh�.
Careful what you wish for, careful what you do
Even when you whisper, someone's listening to you
Careful what you wish for, careful what you say
Careful what you wish for, 'cuz it just might come true someday
http://www.jonathabrooke.com/music/careful-wha t-you-wish-for/careful-what-you-wish-for