The same line may read as "You are a f*ckup failure as a human being and professionally alike... and people die and will die. Because of it. Because of YOU."
I think that's what is so hard for others to understand. The level of responsibility is enormous - and when you screw up it can be catastrophic. So you go into hypervigilent "gotta save them" mode.
We know it doesn't make sense because the threat is gone. But.
Then it just becomes waiting for the next one. Thats part of the fun of ptsd. You KNOW how badly things can go - so you have to make sure it won't even if the environment you are in is completely different.