The author Laura Vanderkam, who writes books about making the most of the time you have, shares a hot tip about using your weekends well: Plan your days off. That little tidbit sometimes rattles around my brain at 3 pm Saturday afternoon when the only thing I’ve done of note for the day is scrub a toilet. My father believed strongly that weekends were for outings (Disneyland! Universal Studios! The beach!). Why do I so often go to bed Saturday night suffused with regret about wasting my oppo...