By telling your child they’re smart, you unintentionally send the message that they’re only smart when they get good grades or accomplish a goal. Studies have shown that when we tell kids they’re smart after completing a puzzle, they’re less likely to attempt a more difficult puzzle after. That’s because the kids are worried that if they fail, we’ll no longer think they’re "smart.”
Instead, try telling your child that you appreciate their effort. Sure, solving the puzzle is fun, but so is attempting a puzzle that’s even more difficult. Those same studies showed that when we focus on the effort, kids are far more likely to attempt a more challenging puzzle the next time.