The Catechism of the Catholic Church teaches us about the state of purification called purgatory (paragraph 1031). Nothing evil is allowed in Heaven. Jesus’ sacrifice is all transforming, not just a “cover
up.” What I mean by this is that we believe that Christ’s sacrifice is not just making us appear to be pure, but when we really accept Him wholly we are transformed. We just need to receive Him.
As imperfect, fallen humans, we might likely not enter into eternal life completely spotless, and that is why His love continues to purify us in the state of purgatory. What’s left of sin is taken away. Traditionally, people ask for 40 Masses to be said for a person who has passed. Forty biblically represents a long time, so people were aiming to help someone even if that person was said to be in Purgatory for a long time.
The afterlife doesn’t necessarily have a sense of time, so when someone speaks in manners of time, it’s just us finite humans attempting to understand the afterlife. We should prepare ourselves to be rid of all sin as soon as possible through prayer, the sacraments given by God, and constant conversion. That way, we can enjoy the Kingdom of Heaven where we all belong “sooner”—so to speak.
Until then, we still strive to understand and visualize purgatory. For example, Dante’s famous Divine Comedy is a poem about a character’s journey through heaven, hell, and purgatory. If you want to understand Purgatory better,
Prayer for the Faithful Departed: Eternal rest grant unto them, O Lord, and let perpetual light shine upon them. May they (or the souls of the faithful departed), through the mercy of God, rest in peace. Amen. *According to the Enchiridion of Indulgences #46 (1908) and the Raccolta #582 (1927), this prayer is graced with a partial indulgence for souls in purgatory.
Prayer for the Holy Souls in Purgatory by St. Gertrude the Great:
Eternal Father, I offer You the most precious blood of thy Divine Son, Jesus, in union with the Masses said throughout the world today, for all the Holy Souls in Purgatory, for sinners everywhere, for sinners in the universal Church, for those in my own home, and in my family. Amen.