There is a tradition that Ph.D. students get three balls and they have to learn to juggle before finishing the Ph.D. In fact, learning to juggle is supposed to contribute to the Ph.D. work. The precise relation has to be figured out by the person in question, of course.
Hear, hear! We could also let them have the sole responsibility for a family including at least one small child for a year. Perhaps even 6 months would be enough. Afterwards they would be so relieved to get back to the relaxing task of a doctorate program nothing would feel daunting ever again.