My graduate advisor is 60 years old, and his hair is still jet-black and thick. We asked him for his maintenance secret, and he said: I never worry about anything. The things of the research group are handled by my students. The things at home are handled by my wife. My only task is to stay alive. I said: Does that count as being a “hands-off manager”? He said: That’s called “scientific birth control.” Worrying makes you lose hair; not worrying means you don’t. Hair and worries—you can only keep one. That was the first time I knew what it means to be “heartless and carefree.”