Let me ask you one question,which sin did God not forgive?none,hence no one is above this law,the husband might have cheated on the wife but that should not lead to a separation.The wife should talk to the husband so that she may know where the problem is arising from,why this,why that questions will be answered...
Also the wife should not forget to bring the husband before the Lord in her prayers,she should pray for her husband to be faithful to her and keep away from the lust of flesh,this will offer a suitable solution that will not cause her pain in later times.....
The reason i posted this is because i have seen most people who suffer from this problem. It becomes worse when it even affect the children.
One woman who is now separated with her husband, does not want her children to see their father at all, because she claim that she was thorouly abused by this man.
It became worse when one of her children was getting married. The girl wanted her father to attend her wedding, but the mother said, 'if your father is coming to your wedding, then i will not be there.' what a tough situation life becomes, due to lack of forgiveness.
exactly,that is the pain of vengeance....
Study a little deeper on this.
"But Joshua said to the people, "You are not able to serve the Lord, for he is a holy God. He is a jealous God; he will not forgive your transgressions or your sins.  If you forsake the Lord and serve foreign gods, then he will turn and do you harm and consume you, after having done you good." Joshua 24:19-20 (ESV)
This theme goes all through the scriptures. The sin that God will not forgive is the sin that we do not ask to have forgiven. Repentence and conversion is a prime prequist for forgiveness and restoration. Before you make such strong statements, it would be well to have inspired backing for it, not just your opinion.
"Therefore I tell you, every sin and blasphemy will be forgiven people, but the blasphemy against the Spirit will not be forgiven.  And whoever speaks a word against the Son of Man will be forgiven, but whoever speaks against the Holy Spirit will not be forgiven, either in this age or in the age to come." Matthew 12:31-32 (ESV)
Ya... For example my sons father was abusive, and a drug addict. I have not spoken to him in 8 years and do not intent to, because the core of the matter is that I do forgive him, and weep often for his sake hoping that he gets him self straightened out, and comes to the foot of the cross, but I can not risk the physical or emotional safety of my children...
In many ways I have considered him dead for many years now, because I knew it was the drugs and alcohol that made him that way.. The man I walked away from was not their father... I know you may say "He could clean up you should give him a chance to be around the kids." I gave him three and sadly his addiction is to powerful.
That being said I think what it boils down to is you can forgive someone and even weep for them no matter how many times they burn you, but you can't always trust them again..