Some years ago, I went through a dark time that ultimately taught me about light.  It began one winter with a vague gloominess that I assumed would just go away. Instead, it got worse. By springtime, when life around me was bursting with renewal, I was mentally shriveling. At night, I felt anxious and slept fitfully or not at all. Come daybreak, I could hardly get out of bed.

I had a spiritual foundation for this practice, one that took it beyond positive thinking—my study of Christian Science.

I was away from home, guest teaching at a small college. Three weeks into the semester, when I’d sunk to what felt like my lowest point, an old friend arrived on campus to give a lecture, and he phoned me to set up a visit. Normally, an opportunity to see him would have filled me with joy. But I could hardly muster the energy to greet him. He invited me to take a walk just beyond the campus through farmlands atop limestone bluffs that rise from the banks of the majestic Mississippi River.