O My Jesus,
forgive us our sins,
save us from the fires of hell,
and lead all souls to Heaven,
especially those most in need
of Thy Mercy.
When I first learned this prayer (in adulthood, by the way) I found it to be so very comforting. When we pray for "those most in need of (God's) Mercy", what is it we are praying for? We are praying for God to send to Heaven, those who we find the most irksome. Those who we stay up at night worrying about. Those who seem to drive us again and again to sin. Those whose names we can hardly stand to speak.
What a relief that is! Instead of harboring all kinds of hatred and resentment towards those people, or allowing our lives to be ground to a halt with unproductive anger or worry over them, we offer their souls up to the Lord. How spiritually freeing that is!
This prayer, by the way, is the Fatima prayer, said after each decade of the rosary. This prayer was given to the children of Fatima by Our Lady during her third apparition there.