This is the memorial of Saint Callixtus, (+222-223), a reformed slave who seems to have lived a rather dissolute and rebellious life in youth, with theft and street fighting as part of his resume. He was soon arrested – as a Christian of all things – and sent to the mines of Sardinia, but was mercifully released sometime before the turn of the century. In all the turmoil, he had at some point reformed, and was ordained a deacon in 199, being put in charge of the cemetery on the Appian Way, the first plot of land officially owned by the Church, apparently. The catacombs there still go by his name.
His talent and energy recognized, he was two decades later, 217, chosen as Pope, extending the mercy shown to him to others, allowing schismatics and others into the Church with little or no penance. The rigorists demurred, and chose Hippolytus as anti-Pope (who also later was sent to Sardinia, repented and reconciled, and was canonized – there’s something about Sardinia).
Or, rather, there’s something about suffering, which, as Pope John Paul teaches in his profound letter on this theme, prompts an openness to God’s mercy and His salvific grace within the soul. All God needs is a movement of the heart towards Him, just a nudge; that is enough, to make a saint, or two. Or myriads.