I recently came across this article from Scientific American Mind that dates back about a year and a half but is no less timely. Thirty years of research has shown that a focus on effort - not on intelligence or ability - is key to success in school and in life.
"When we gave everyone hard problems anyway, those praised for being smart became discouraged, doubting their ability. And their scores, even on an easier problem set we gave them afterward, declined as compared with their previous results on equivalent problems. In contrast, students praised for their effort did not lose confidence when faced with the harder questions, and their performance improved markedly on the easier problems that followed."
The conclusion - don't tell your kids how smart or gifted they are. Instead praise them for their hard work.