Tell a stranger that you talk to yourself, and you're likely to get written off as eccentric. But the truth is that we all have a voice in our head. When we talk to ourselves, we often hope to tap into our inner coach but find our inner critic instead. When we're facing a tough task, our inner coach can buoy us up: Focus—you can do this. But, just as often, our inner critic sinks us entirely: I'm going to fail. They'll all laugh at me. What's the use?