Those Catholics who are parents may understand some of the ideas on this brief posting. A friend of mine could not understand why purgatory is punishment. She could understand the formation and healing of the soul in purgatory, but could not understand the punishment part.
When we sin, there are two consequences. Let me backtrack by reminding you that formation is the growth in the Spirit in the life of the virtues. Even a child can become a saint through formation. When one sins, two things happen: one leaves the road of formation and falls off, as it were and one incurs a consequence of that sin. There is a consequence because God is All Just, Loving, Pure, Innocent and Merciful. If we truly knew Him as He is, we would not be able to sin, at least so easily.
So, formation is interrupted by sin and sin causes a rupture in the person 's relationship with God. This sin must result in a reparation. There must be penance, which is an inconvenience and even a pain for us. Too many penances in the Confessional are not painful. Perhaps, going to Confession is a penance, because we are so proud. Making a good Confession can be a penance, as one must not cover up sins.
So, formation and the consequence of sin leads to the need for both restitution, which has been earned by Christ Himself, but we enter into this, and by some penitential act.
Purgatory exists because we did not follow up all the opportunities for grace which we could have done in our lives. The real road to holiness means that we allow God to purify us on earth. The real goal is heaven, not purgatory.
I suggest that readers study the sections in the CCC about merit and justification.
