A bitter critic is the sweetest corrector.

Is constructive criticism really constructive? Not really. You can't make a child better by pointing out what you think is wrong with him or her. Criticism either crushes spirit or elicits defensiveness. Constructive criticism is an interesting combination of words. "Construct" means "to build." "Criticism" means "to tear down" It creates defiance and anger as well.

Constructive criticism is good but from the right people and not from any Tom, Dick and Harry.

¿No sabéis quiénes son los críticos? Aquellos que no han tenido éxito en la literatura y en el arte.

Being a critic is easy.
But if the critic tries to run the operation, he soon understands that nothing is as easy as his criticisms.
Criticism without a solution is merely an inflation of the critic's ego.

I do not take constructive criticism from people who have never constructed anything.