Have you ever seen a mother come up and smooth the hair of her older teenager, to the chagrin and irritation of the teen, who says, “Come on, Mom, I’m not a kid anymore.” It’s an awkward moment: The parent has failed to recognize that overseeing her child’s appearance, once a good practice, is now inappropriate. It is common sense that parents must adapt and change their roles as children grow up. But what about CEOs, who may be hired for one task, but face an entirely different one years or even months later? The secret to long-term CEO success, suggests David Nadler, a consultant to boards and senior executives, is conceiving of a CEO’s tenure as a performance with a series of distinct acts. “Each act requires the CEO to lead, think and behave in fundamentally different ways.…