All of the prayers given by the Blessed Mother and the Angel of Peace/Portugal at Fatima to the world via three children in 1917 are astoundingly revealing, but especially (to me) the one Mary asked them/us to pray after each decade of the Rosary’s mysteries:
O my Jesus, forgive us our sins, save us from the fires of hell; lead all souls to Heaven, especially those in most need of Thy mercy.
Who is in most need of His mercy? Thankfully, that is not up to us to judge; however, judging the condition of souls and weighing who may be in dire spiritual danger are two vastly different things — or we’d have heard nothing of this prayer.
Also, we aren’t praying this because someone holy told us to; we’ve been given a part in transformation — actively called to actively love — and it requires humble, selfless, merciful considering.
Even though this is a private prayer, and we don’t ever have to fill in the blanks (the Lord knows the who, what, when, where, why and how of all), if we happen to think of someone we feel is in great need of His mercy, or one (or more) who truly needs leading to Heaven having never found the road or fallen off of it or been deviously misled, we can and perhaps should mentally bring him or her or them into this holy prayer. (It cannot possibly hurt anything. Love, on the other side of the veil, is a shorter, clearer word: we.)