That’s Heidi Halvorson’s advice:

When you are an expert, and you already more or less know what you are doing, it’s negative feedback that can help you do what it takes to get to the top of your game. I’m not suggesting that you never tell the rookie about his mistakes, or that you never praise the seasoned professional for her outstanding work. … But I am suggesting that piling on praise is a more effective motivator for the rookie than the pro. And I’m saying, point blank, that you shouldn’t worry so much when it comes to pointing out mistakes to someone experienced.