It Doesn't Happen Very Often
Mentally healthy people don't hit, push, punch, or throw things at loved ones who could be seriously hurt.
Mentally healthy people do not ever have sex with an unwilling partner through force or threat.
Mentally healthy people don't load their kids or their spouse into the car and drive drunk.
Mentally healthy people don't stay in the vicinity of those they love when they cannot control their angry words or actions.
Mentally healthy people don't have unprotected sex with someone who might be infected with HIV, HPV, herpes, syphilis, or gonorrhea and then go have sex with their life partner.
Mentally healthy people don't blow the mortgage money or food budget on betting or shopping for things they don't need.
They don't. They know how to stop themselves, and they stop themselves before they do something that could hurt those they love and cause them great shame.
Mentally unhealthy people do these things, feel ashamed, and promise it won't happen again. When it happens again, they invent stories about why they did what they did. These stories usually involve blaming their victim. It reduces their shame.
What mentally unhealthy people need is not a second chance or a third or a fourth. They need help finding the courage to get mentally healthy, to admit they need to learn new approaches to old problems, to do without the alcohol or drugs they are sure they cannot live without, to get surgery to remove a brain tumor or bleed, to take the drugs that will stop cravings or thoughts they cannot otherwise control.
Even if the awful consequences don't happen very often, these people are mentally unhealthy all the time. Living with this takes an awful toll on the mental health of everyone around them, because no one can predict when the fear and the shame will return. Children grow up anxious and with no basis for trusting others. Spouses grow overly cautious and self-protective. Those with the problem may start to see their spouses and children as the problem, because the consequences would be less without all the shame of hurting loved ones.
Not every mental health problem can be cured or managed, but many can. It takes courage, though, to choose to get treated. It may take even more than allowing an amputation or a mastectomy or a prostatectomy. To find this courage when death is not the alternative, it helps to know it is their only option to keep their loved ones in their lives. Second chances say otherwise.
It is definitely not easy to separate to protect you, your mentally unhealthy mate, and your children while your mate finds that courage. It is often very expensive. It requires protection from an out-of-control reaction. It calls for lots of support for you and the children. This, too, takes courage.
Many wait to find their courage in the anger that propels them toward divorce. This is understandable, but the message it sends comes out a lot like this: "I no longer see you as a man or woman with a treatable mental health problem that affects all of us but as a defective individual not deserving of love." Not many of us would find the courage for an amputation if told we would die with or without one.
"It doesn't happen very often" is the first step to writing someone off as a defective person who cannot be loved. If it happens even once, it's a serious problem. If it happens again because neither of you took precautions to prevent it from happening, the second step is likely to be a very slippery one that hurts both of you and any children you share.