The Drywall Parable:
Sam and Sue were having a disagreement over the color of the drapes. Sam got so overheated in the disagreement that he put his fist through the drywall next to Sue’s head. Later, he apologized for loosing his temper and punching a hole in the wall. Sue told him that she forgave him.
Does the fact that Sue forgave Sam fix the hole in the wall?
No, that would take further steps–presumably from a repentant Sam–to repair what he damaged.
Does the fact that Sue forgave Sam mean the drywall will be the same again?
No, that wall is broken, and will need replacement.
Does the fact that Sue forgave Sam mean she ought to forget Sam lost his temper and became violent?
No, it would be unwise and unsafe on her part to forget such an incident.
Does the fact that Sue forgave Sam fix the original problem of Sam’s sinful lack of self-control?
No, Sam still needs to work on this so that it does not happen again.
When a faithful spouse forgives an adulterous spouse, that forgiveness does not erase the consequences or damage done by the adulterous betrayals. The cheater still has to do work to repair what he or she destroyed on top of apologizing and securing forgiveness.
When a faithful spouse forgives an adulterous spouse, that forgiveness does not mean the marriage will be the same as before now. A complete restoration or resurrection process will need to happen.
When a faithful spouse forgives an adulterous spouse, that does not mean the faithful spouse ought to forget what happened and that their spouse is capable of adulterous betrayal. That would be unwise as God gave us memories for our own safety, and so that we may learn from our past.
When a faithful spouse forgives an adulterous spouse, that forgiveness does not solve the original marriage problem–i.e. the cheater’s lack of character. The cheater must work on this demonstrating true repentance for the marriage to have any hope of Godly restoration.