Criticism at the wrong time, even if it's legitimate criticism, can be seriously damaging and make the writer lose faith in what he's doing. It's the timing that's all-important.
Donna TarttThe firelight magnified our shadows, glinted off the silver, flickered high upon the walls; its reflection roared orange in the windowpanes as if a city were burning outside. The whoosh of the flames was like a flock of birds, trapped and beating in a whirlwind near the ceiling. And I wouldn't have been at all surprised if the long mahogany banquet table, draped in linen, laden with china and candles and fruit and flowers, had simply vanished into thin air, like a magic casket in a fairy story.
Donna TarttI think it's especially important for an editor to say what he's enjoying. For a novelist to be told, midstream, what he's doing right can actually influence the unwritten parts of a novel in a positive way - praise helps a writer know what's good about what he's written, what's interesting and exciting, and what to work for in writing the conclusion.
Donna Tartt