Though it's clear that too little praise can be extremely damaging for a child, research indicates that praising kids too much can be damaging, too. Studies have shown that praising kids for their intelligence can actually make them less motivated at school, because they start to assume that everything should be easy for them to learn. Then, when confronted with things that are difficult for them to learn, they either become overwhelmed and give up or choose to study something easier.
The type of praise a child gets is important as well. Children older than age 7 are extremely sensitive to insincere praise, and if they receive a lot of it, they start discounting sincere praise as well as insincere praise.
Children who are over-praised or praised only for their intelligence also report being more willing to lie about their grades or cheat to get a good grade in order to keep up the appearance of being smart.
Praising kids for their effort, rather than for their intelligence, makes them more motivated to learn and even encourages them to choose to learn more difficult things.