At the beginning of his pontificate, St. John Paul II let everyone know that the Rosary was his favorite prayer.
Aleteia.org - by Philip Kosloski
Popes don’t always reveal their personal preferences in public, but St. John Paul II wasn’t afraid to reveal his favorite types of prayer.
In the second Angelus message of his pontificate in 1978, St. John Paul II said plainly, “The Rosary is my favorite prayer. A marvelous prayer! Marvelous in its simplicity and in its depth.”
St. John Paul II affirmed this statement in his Apostolic Letter, Rosarium Virginis Mariae in 2002, pointing out how he revealed this aspect of his spiritual life so early on in his pontificate and how it continued to comfort him in good times and bad.
The Rosary has accompanied me in moments of joy and in moments of difficulty. To it I have entrusted any number of concerns; in it I have always found comfort. Twenty-four years ago, on October 29, 1978, scarcely two weeks after my election to the See of Peter, I frankly admitted: “The Rosary is my favorite prayer.”
In a certain sense, if you want to know all the reasons why St. John Paul II loved the Rosary, all you need to do is read Rosarium Virginis Mariae. It contains an in-depth study of the Rosary and the many reasons why the Polish pontiff loved it.
St. John Paul II does list one of the primary reasons why he loves it, explaining how the Rosary is a path of contemplation.
[T]he most important reason for strongly encouraging the practice of the Rosary is that it represents a most effective means of fostering among the faithful that commitment to the contemplation of the Christian mystery, which I have proposed in the Apostolic Letter Novo Millennio Ineunte as a genuine “training in holiness”: “What is needed is a Christian life distinguished above all in the art of prayer” … The Rosary belongs among the finest and most praiseworthy traditions of Christian contemplation.
For St. John Paul II, not only did the Rosary provide a way to contemplate of the mysteries of the Gospel, it also looked to Mary, whom he believed was a “model of contemplation.”
St. John Paul II did all that he could to promote the Rosary during his pontificate, sharing with the world its impact on his life, hoping that it could help us in our own spiritual journey.