I did it, I thought in disbelief, and I even sprinted at the end. Did anyone notice, I wondered. I somehow managed to find it in me to sprint across the finish line. Then I tried not to collapse right there on the road.

My body ached, and after hours of sweating, I was quickly becoming chilled in the 50-degree wind. Desperately trying to keep moving, I suddenly found myself in a crowd of post-marathoners shuffling slowly, cattlelike, along a barricaded corridor, as volunteers handed out water and enshrouded us with thin mylar blankets and then others handed us medals, all alike, to commemorate our run.

This should have been my greatest hour. After all, I had secured the grail of marathons, the holy Boston, something I had been dreaming about for years. Yet it seemed strangely pointless, so after-the-fact, so anticlimactic. And then it dawned on me. Finishing the Boston Marathon was nothing in comparison to the real hurdle I'd been able to surmount and the one that had turned me into a runner in the first place: major lifelong depression.

Long before Boston, in fact, running had saved my life.