When to Stop and When to Keep Going

The challenge of the amateur is to know when to stop and when to push through.

I still remember what became known as the most challenging run of my life … twenty excruciating miles. It was a few weeks before a marathon I’d promised to complete, and I simply had to extend the distance of my weekend long run. (A marathon is 26.2 miles, and you can usually complete it without training the full distance, but you shouldn’t train any less than twenty miles.)

As I wrote at the time, nothing went right...