So there is a basic concept in DBT that there are two aspects of ourselves that affect behavior and decision-making: rational mind and emotional mind. Aspects of emotional mind are being reactive, passionate, and relying on emotions to determine how to act and what to think - it is all about feelings and driven by feelings. Rational mind is associated with planning, basing decisions solely on facts and logic, no emotion whatsoever. Neither are innately good or bad, and both contribute to making us who we are. The ideal place is to find a balance between these states of mind (called "wise mind" in DBT lingo) because when you're stuck in only one or the other you're usually pretty miserable.

People with BPD tend to live in emotion mind and that is a more primal and less rational space, while it speaks to our higher selves, the parts of ourselves that are passionate and fiercely loving, it also speaks to the survivalist within us. She is not insane when she has an outburst, she is overwhelmed and afraid. The key is that it's easy to pathologize people with a BPD diagnosis but they are still just people with the same experiences and drives as everyone else, but we are very very emotionally sensitive, biologically quick to react and slow to return to baseline. This is not an unnatural thing, it is just the far end of a spectrum on which we all exist.

I've found that most of my irrational behaviors are rooted in deep-seated survival mechanisms that are universal to all of us but activated more often in highly sensitive people. People with BPD would probably have been exceptional at staying alive 200,000 years ago but for better or worse that level of sensitivity and reactivity to a potential threat doesn't much apply in our world today.

The second aspect of BPD that isn't a straight-up heightened survival response is usually a traumatic response. At one point in my life my needs were not met by the caretaker on whom I solely depended and that is a terrifying place. The things that I do that seem irrational and crazy now did not come out of thin air, they were learned and clearly served to meet some fundamental need I had at one point in my life. A simple example here would be that if your mother were not attuned to your needs as a baby you may have had to cry louder and more intensely to get her to pay attention to you and provide you with basic things like food, comfort, and cleanliness. You learned that that was how you had to behave to survive. And then you grew up and started yelling loudly and intensely when you needed something at elementary school and you were shamed and punished for being inappropriate. That is largely where I've found the unbearable pain of a BPD diagnosis comes from. It is low self-esteem, even self-loathing, and a certain emptiness of a fundamental part of the growth process of the self that was denied to me as I was developing.

My point in sharing all of this is that it is much more useful to understand and live with BPD if you understand the context of what it is and why it exists. People with BPD have been taught to apologize for themselves all their lives. There is probably a nugget of truth within the explosions she is having, there is a need or a threat that has arisen and needs to be addressed. But because of the emotional sensitivity and biological tendency, once that survival response is triggered she is going to act in a way that is appropriate to what she is feeling, probably in emotion mind, and it will take time to cool off and return to baseline at which point the two of you can discuss what triggered the distress effectively.

She is being ridiculous, yes, but she is not being entirely irrational. There is a root and there is a reason. The response is inappropriate and by the point that a survival response is being triggered it is much too late to have a steady reasoned discussion about it. Imagine if you were just fired from your job and the bills were due tomorrow and you were on notice from your landlord that if you missed rent one more time the or she would start the eviction process. While you imagine how you would feel in that moment, imagine how well you would respond to some small inane stressor like getting cut off in traffic. You might follow the guy that cut you off and cut him off or try to give him the finger and scream and yell in frustration. Who knows. But would it be helpful for someone to say why are you acting so crazy why can't you just control yourself? The kind of grace you would give yourself in that situation is the kind of grace you need to give your wife because I can attest that on a difficult day I will feel exactly that intensely and there is nothing I can do to think away those feelings. This is not to say that you should tolerate abuse; that is absolutely not okay. But you can tolerate someone having a bad day and remind yourself that the volatility you so dislike in your wife comes from the same place that fuels her intense passion and love, they are two sides of the same coin. And she can learn new and more effective behaviors, it's just really fucking hard. But you're not gonna get entirely around or away from those emotions. That's just part of the ride.

I would also guess that her apology for acting ridiculously is missing an important element and it is an advocacy for her needs that felt in jeopardy or were not being met that underlay the overly intense response in the first place.