From the time we learn to speak, we're told that if you don't have anything nice to say, don't say anything at all. When you become a manager, it's your job to say it -- and your obligation. Author Kim Scott was an executive at Google and then at Apple, where she developed a class on how to be a good boss. Radical Candor is a simple idea: to be a good boss, you have to Care Personally at the same time that you Challenge Directly. When you challenge without caring, it's obnoxious aggression; when you care without challenging, it's ruinous empathy. When you do neither, it's manipulative insincerity. This simple framework can help you build better relationships at work, and fulfill your three key responsibilities as a leader: creating a culture of feedback (praise and criticism), building a cohesive team, and achieving results you're all proud of.