> It's not their fault, they didn't choose this. You did.
That's exactly right. You chose it. You chose to be a partner to that person. In the case of marriage, typically that means "in sickness and in health" and so you either step up to the plate and be the support they need, or you realize your mistake and move on before it destroys both of you.
That's the positive (yet realistic) take on what you're saying here, which I hope is your intent.
I'm a little bothered by your characterization of partnership with someone with a mental health condition as "...tiptoeing through the fucking minefield of their emotions..."
Mental health issues are not emotions. They may interplay to a degree, but do not mistake clinical anxiety or depression for someone being excessively emotional. It is a medical disorder of the brain that causes it to malfunction. My ending statement is a bit hyperbolic, but not really: dismissing a mental health disorder as emotions is how people end up dead.