Why Punishment After Confession?

Confession remits the eternal punishment due to sin, but it does not remit the temporal punishment that God requires as satisfaction for our sins. While God is perfectly merciful, he is also perfectly just. It would be an injustice if there were no consequence for sin. As human beings, we also require some form of purification for our sins. Even if we have repented of our sins, the effects of our sins are still out there in the world and affect those around us.