Frank Shorter, 68, won the gold medal in the men's marathon at the 1972 Summer Olympics. He is the author of "My Marathon" (Rodale). He spoke with Marc Myers.

I thought of Joni Mitchell while running the marathon at the 1972 Olympics in Munich - actually I thought of her song, "Big Yellow Taxi," which came out in 1970. The song helped me stay focused while training and avoid what I call the "if onlys" - regrets over not going after something you really want.

My friend Ken Davis turned me on to Joni. Ken and I first met when I moved into Vanderbilt Hall at Yale in 1965. We both were pre-med and we both shared the same drive and ambition. Ken was brilliant, but he also loved rock. We often listened to his stereo system in the suite, which had a receiver that could pick up WNEW-FM in New York. In 1968, you could hear all the best new rock music on that station. In the fall, Mitchell played close to Yale, and Ken insisted we go.

Her music was a soft protest, which matched my view and Ken's perfectly. We didn't get caught up in the campus-revolution thing. Mitchell reinforced our belief that you didn't have to protest overtly, that you could work hard so that in the future, when certain windows opened for change, you'd be prepared to take advantage of them and make a difference.

During my senior year at Yale, I began to show serious running talent. But when I asked if I could postpone med school to compete, the dean said no. So I dropped out in late '69 and moved to Gainesville, Fla., to train and attend law school.

Sometime in the spring of '70, I heard "Big Yellow Taxi" on the radio: "They took all the trees, / put 'em in a tree museum / And they charged the people / a dollar and a half just to see 'em / Don't it always seem to go / that you don't know what you've got / 'til it's gone." Those last two lines resonated, and I sang the song's first two verses whenever I ran.

Today, I still sing "Big Yellow Taxi" to myself. I never told Kenny how I felt about it. Ken - or Dr. Kenneth L. Davis, who pioneered breakthroughs in Alzheimer's treatments - is now president and CEO of New York's Mount Sinai Health System. I've always wondered if the song meant as much to him as it did to me.