Dainty: if one is fully prepared to the point that they can "coolly" ride over a disaster scenario, that would be the ideal and it is attainable. But it is the scenario where one is not fully prepared and where adrenalin does take over, brings up the question, can we prepare for that? What makes a disaster so incredibly horrific is the entrapment; the inability to escape the consequences. We prepare and prepare physically and mentally all the while knowing that there is a situation that could enfold that we would be helpless, perhaps not lethal, but nonetheless beyond our capacity to keep from getting frantic.
Learn to be "okay" with being helpless and entrapped with no way out. It's different than preparing for specific situations because what you're preparing for is a physiological reaction to the sting of no control. My suggestion for training yourself to do this is that next time you find yourself in a situation like that use it as an opportunity to begin creating an internal process whereby you teach yourself that helpless/entrapped = relaxation. It's a strategic retreat, and in the midst of the situation it can feel like you're "accepting" it to stop fighting and give up. But if the fighter is in you, if you want to live, then you won't stay that way, it'll only be a temporary measure.
The picture I often use in my own mind is of someone in aquatic distress. If you could just float on your back for a little while, you'd be okay. In the moment, floating on your back feels like the last thing you want to do - it's
completely counterintuitive, because your brain is screaming at you to struggle, to fight to stay alive. And survival mentality is all about about reinforcing that instinct. But this is where it comes back to bite you. You must learn how to unhinge that instinct if needed, and have a process by which you internally recognize that in order to survive you must do the very thing that feels like the antithesis of survival: give in. Just for a little while. It can be intense enough to feel like you're accepting death, so you may need to work through whatever spiritual and emotional factors you have regarding that in order to set up this internal process.
Once you've come through the other side a few times (assuming you have the opportunity to practice - not everyone is so lucky

), and each time experienced the relief of "it worked, I'm still alive, I've survived", then it begins to create a sort of internal protocol that you can resort to in a variety of desperate situations. The more you manage to do it, the less counterintuitive it feels because you learn that it paradoxally achieves the desired result of survival.
I'll give you an example: I have a medical problem that sometimes causes my airways to spasm shut, without warning. One second I'm breathing fine, I exhale, and suddenly inhalation doesn't work. This can happen at any time, awake or asleep, talking on the phone or sitting at my computer or resting in bed. I estimate these spasms last 10-20 seconds, but it's hard to tell how accurate my sense of time is. The immediate instinct is to fight to obtain air, to strain as hard as humanely possible to expand my lungs again. I've had my chest muscles hurt for days after such incidents just from the immense effort to inhale. I've come close to passing out several times, and the times a friend has happened to be present they're quite shaken.
But here's the thing: if I stop attempting to inhale the moment I realize this is happening, and counteract my instinct to fight for air with the alternative protocol of relaxing and even exhaling further (though my lungs are empty) then the life-threatening spasm resolves quickly. I figured this out by noticing that when I came close to passing out and my body began to go limp then that's when the spasm finally let up and allowed me to inhale. I reasoned that if I could relax instead of fight from the moment it started then it might achieve the same effect. And it did....once I could manage to do it. It took a lot of work to get to that point, starting with less time sensitive scenarios and training myself to optionally switch to this counterintuitive response in any situation where my adrenaline and fighting will to live is kicking in.
It's empowering for me when I come out the other end of a situation where I was helpless and I managed to keep my nervous system parasympathetic throughout. It truly is something that can be applied to any scenario. My instinctive fight or flight response is still there, and if I deem it helpful in a crisis then I allow it to run its course. But if I realize that my instinctive physiological reaction is not helpful, and that the most strategic response is to stop and relax, then I dig up the image of a drowning person in my mind and tell myself, "okay, it's time to float on your back right now. I know it feels opposite of what's helpful, but trust me on this" and I guide myself through that process.
If you have the opportunity to learn this, it's a pretty valuable survival skill, IMO.