From Thomas of Celano’s authoritative “Saint Francis of Assisi:”
“A certain spiritual brother, long in religion, was afflicted with a great temptation of the flesh and he seemed almost sunk into the depths of despair…One day, however, when he was walking with blessed Francis, the saint said to him: ‘…as often as you are tempted say with my permission seven Pater Noster.’ Astonished that the saint knew these things, and filled with very great joy, the brother very shortly escaped from all his trouble.”
This is also similar to the practice recommended by fellow Franciscan and contemporary of St. Francis, St. Anthony of Padua, who asked his followers to recite three Hail Marys: “…to honor the spotless Virginity of Mary and to preserve a perfect purity of mind, heart and body in the midst of the dangers of the world.”
Hundreds of years later, St. Josemaria Escriva wrote: “In your personal prayer, whenever you experience the weakness of the flesh you should repeat: Lord, give the Cross to this poor body of mine, which gets tired and rebellious.”
Author’s note: It’s most interesting in the selection from the life of St. Francis, that the brother who was so plagued with lustful thoughts was a man not new to the religious habit - revealing that no one is immune from the allurements of carnal desires. Yet, St. Francis gives rather basic advice, even to someone who is persuadably spiritually advanced. Similarly, St. Anthony also goes back to prayer - as the greatest weapon against sexual license. Lastly, the Saint of practicality, Josemaria Escriva, didn’t swerve far from the counsel given by his illustrious predecessors. In short, when faced with sexual temptations, keep it powerful and straightforward - got to The Father, and the Son, and then to His Holy Mother.