In “Lost in the Cosmos: The Last Self-Help Book,” Walker Percy writes, “Johnny Carson, when questioned about his aplomb on the stage before a TV audience of millions, replied: ‘Sure, I’m at ease up there—because I’m in control—but when I’m at a cocktail party and caught in a one-on-one conversation: panic city!’” In his book of essays, “Wind-Sprints,” Joseph Epstein recounts an incident from the life of John Keats when the poet took a two-mile walk with Samuel Taylor Coleridge, “one of the famous talkers of his day.” In a letter to his brother, Keats wrote: “I heard his voice as he came toward me—I heard it as he moved away—I heard it all the interval—if it may be called so.” Regarding conversation, most of us probably find ourselves in the middle of these two extremes. Perhaps we do just fine when talking one-on-one with a friend, but clam up …