Not OP, but perhaps the regret is about putting too much pressure on themselves, not the aftermath. We owe it to our loved ones as much as to ourselves to keep a healthy balance in the things we do.
There is that, but I also don’t feel like “I was crazy” entirely absolves me. I could have made some better decisions for sure.
No-one ever gets every decision right. My fuckups have been lucky and haven't impacted my life too much. Your fuckups were unlucky in that they've interacted with an existing condition and thrown your life around a heap. That doesn't mean you're inferior to anyone, or have any worse/better judgement, it just means you drew a short straw. :(
Sure, we all make mistakes. But I think it's healthy to look back on those with regret rather than just shrugging it off. It's hard (even harder) to change otherwise.
Doing better doesn't mean you have to regret things. You can just accept you weren't perfect, understand you now know better (but still not perfect), and move on.
but that's like saying we owe it to our loved ones to never get sick. Mental illness is illness, it's not something you are doing to yourself.
There are different types of illness. Some can happen, and there's nothing we can do about it. That's not the same as engaging in behaviour that causes illness. Self-destructive behaviour chips away at our physical and mental soundness. If we fail to regulate our actions in time we invite illness. We certainly owe it to our loved ones to avoid that.