Here’s a nice article, The Power (and Peril) of Praising Your Kids — New York Magazine, relating some psychological work which I’ve always tried to explain to my relatives and friends that were parents. i.e. I’d rather be hardworking than lucky and I’d rather be lucky than smart. Drive, perseverance, resiliency are so much more important than any innate abilities or aptitudes one starts out with.
Bottom line: Praise effort, not intellect. And emphasize the motivatee’s process, not the motivatee’s abilities.