I want to run a half-marathon. There, I’ve said it. I’ve spoken it aloud and placed the intention firmly in the tangible realm. (The intangible realm is reserved for other, lesser desires, like watching The Irishman or learning to grill.) Here’s the rub: I’m a crap distance runner. The distance isn’t the problem, per se—I’m comfortable with hourlong runs, punctuated only by the occasional frantic shuffle to the CVS bathroom. The problem is the speed. Per Runner’s World, the average female runner conquers a half-marathon at roughly 10:29 minutes per mile. My current distance pace is closer to 13 minutes...