Why has the Peace Prayer of St. Francis enjoyed an unparalleled popularity in the past 100 years? Why do princess and pauper, bishop and bellhop, saint and sinner turn to it in emotionally charged moments of life?A number of years ago, while preaching a retreat to some Franciscan friars in Pennsylvania, I got a possible answer to those questions from a surprising source: a young friar, thirty years my junior.

Brother Angelo had been in the Franciscan Order for five years and, by his own admission, was “a big fan of the Peace Prayer.” He was well aware that St. Francis did not compose the prayer “and that doesn’t bother me in the least. I still pray it slowly every single day and let the words wash over me. By trying to put this prayer into action, I feel like I am training my soul to be both a healthy disciple of Jesus and a faithful follower of Francis.”

Holding a master’s degree in physics, Brother Angelo enthusiastically added, “I just love the physics of the Peace Prayer!”

“The physics of the Peace Prayer? What do you mean?”

This prayer challenges the spiritual laws of our human nature. Because of sin, my natural inclination is to focus always on myself. I tend to be self-absorbed and self-centered. I fuss about me, my desires, my wants, and my demands. I can’t break free from the ego’s strong gravitational pull.

I liken it to what is called in physics the centripetal force. If you put a stone on a string and whirl it around your head, the string is constantly trying to pull the stone toward the center. I’m the center, and life is all about me.

The second part of the Peace Prayer is a reminder that it’s not about me being the center and not about being consoled, understood, or loved. It’s not about me receiving or being forgiven. The prayer shapes the contours of the soul to forget the ego and be selfless—that’s how you cross the finish line to eternal life.

Physics also deals with what’s called the centrifugal force. The stone on a string that you are whirling around your head is always trying to break free and move beyond the center. It’s as if it wants to break free from the gravitational pull of the self and move outward and beyond.

That’s really what the first part of the Peace Prayer is all about. It trains the soul to look outward and beyond, to be sensitive to every situation, and to bring whatever is needed to help those who are injured, doubtful, depressed, or struggling to find light or joy. Service—the point of the first stanza of the prayer—leads to selflessness—the point of the second stanza of the prayer—and vice versa. That’s how the two parts of the Peace Prayer are related.

That’s why I am a big fan of the Peace Prayer even if St. Francis didn’t compose it. It not only gets me in spiritual shape by focusing my attention on others but also keeps me in shape by challenging me to die to my natural inclinations.

Athletes talk about being in the zone; when I’m doing selfless acts of service and not thinking about myself, I’m in that sacred zone where God fashions his instruments.

Cleverly combining physics with athletics, Brother Angelo’s explanation revealed the perennial attraction and appeal of the Peace Prayer.

My book, Soul Training with the Peace Prayer of Saint Francis, will show you how this simple prayer can train the soul and keep you in shape until you cross the finish line into eternal life. Think of this book as your workout manual that offers encouragement to condition all the muscles of the virtues to help you stay spiritually fit: faith, hope, love, forgiveness, joy, consolation, understanding, and selflessness.