Many have repented and returned to the way they were because their repentance was not deep.
But those who deeply repented, they never returned to sin again, as we have discussed this issue before here on st-takla.org in other sections. Repentance was a crucial point in their lives, from which they gradually progressed to grow in the life of righteousness, until they reached high degrees of Christian perfection, like David the Prophet in his contrition and tears. And Augustine who became a monk and then a bishop who defended the Christian faith. He had very deep spiritual contemplation. Also Moses the Black, who grew in love and meekness and serving people and became one of the Desert Fathers. And Mary of Egypt who rose high in the life of seclusion and became a hermit and blessed St Zosima the priest.
Those who have sins which they repeat at every confession, they have not repented yet...
And those whose repentance does not include the feelings of contrition, remorse and unworthiness, they have no depth in their repentance, and how easy they go back to sin. Likewise, those who in their repentance, they hasten to the life of joy, before their repentance fully develops and bears fruit.