there is a story of a complaining parents :

we have tried all measures possible to get tour boys to change those awful ways, they did wrong and deserve punishment, don't they?
sometimes we refuse to give them food,and beat them, or mostly we speak sternly about this way of living to them in private, that is the best of constructive criticism I could give, but all this medium did nothing, I mean virtually nothing.
Then we decided to try admiration, we praised only the good things they did, and you know how difficult it is to see something good, when you've already written that person off, but we tried our best, little by little, they now wanted to live up to the expectations of our praises, Now it works like magic, though everything isn't as perfect as we want, our boy now live the good lifestyle expecting our commendation, and we do not hold back we give it lavishly.