Echoes something I read in Dan Coyle's "The Talent Code" – they probablly quote the same study – praising children for their effort had a positive effect, whereas praising for intelligence (an innate quality) had a negative effect. FTA:
The children were randomly assigned to two groups, both of which took an age-appropriate version of the IQ test. After taking the test, one group was praised for their intelligence – “You must be smart at this,” the researcher said – while the other group was praised for their effort and told they “must have worked really hard.” […] The final round of intelligence tests was the same difficulty level as the initial test. The students who had been praised for their effort raised their score, on average, by 30 percent. This result was even more impressive when compared to the students who had been praised for their intelligence: their scores on the final test dropped by nearly 20 percent.