Quit working for them and now I'm a freelance dev.
They asked me to get back on the project and I said fine, that'll be €700/day. After some grumbling they realized they had no other option so they agreed.
The project is still failing due to bad management but I no longer care. I believe to now feel the same sense of calm around chaos and failure like you do.
A lot of developers have real mental scars from bad projects like this, because they get duped into thinking it's a matter of personal pride to see it trough.
It's not. Your primary concern should always be personal health.