I fully expect my wife to extend no forgiveness if I were to be unfaithful to my marriage vows. Whether she would or not is another matter, but rationality would suggest that she withdraw her trust and that would be the end of marriage in any real sense. Any relationship requires fidelity at some level. From my time in Rwanda I recall a pastor who was unfaithful to his wife while serving in another country. When it became known, he apologized, asked for forgiveness, and was moved into administration. He then went on to commit an immense financial fraud, and to continue to be unfaithful to his wife. I made a mental note to myself to not extend any grace whatsoever to a person unfaithful to their marriage vows.
So, I confess that's my zero-forgiveness approach to infidelity. Its a bit like the Old Testament Jewish approach, save for the messiness of that stoning business.
Consider, for a moment, the slightly more flexible Islamic approach.
Imran b. Husain reported that a woman from Juhaina came to Muhammad and she had become pregnant because of adultery. She said: I am pregnant as a result of Zina. Muhammad said: "Go back, and come to me after the birth of the child". After giving birth, the woman came back to Muhammad, saying: "please purify me now". Next, Muhammad said, "Go and suckle your child, and come after the period of suckling is over." She came after the period of weaning and brought a piece of bread with her. She fed the child the piece of bread and said, "Oh Allah's Apostle, the child has been weaned." At that Muhammad pronounced judgment about her and she was stoned to death.
Now, consider the New Testament approach, as reflected in Jesus' response to the woman caught in adultery. 'Neither do I condemn you. ... Go and sin no more.' (John 8:11).
It would appear that I have something to learn about the redemptive power of forgiveness, and the hope against evidence that springs from [God's] intense love for those that don't live up to their covenant vows.