A friend of mine had resisted efforts to get him to run with our jogging group until his doctor told him he had to exercise. Soon thereafter, he reluctantly joined us for our 5:30 am jogs on Mondays, Wednesdays, and Fridays.

After a month of running, we decided that my friend might be hooked, especially when he said he had discovered what “runner’s euphoria” was.

“Runner’s euphoria,” he explained, “is what I feel at 5:30 am on Tuesdays, Thursdays, and Saturdays.”