Neil Armstrong, Neal Stephenson, Neil Gaiman

You manage it by being experienced in what you are doing, ironically.

I am not sure on developing it, but I am good in crisis and can describe what goes through my mind.

A problem is realized. A sense of urgency develops. Assessing as fast as possible the severity, the higher the severity the less assessment needs to be done vs. moving to solving and acting.

Look for the root cause of the problem vs. effects and think of two or three routes of action, quickly. Think ~two logical steps down each route to rule out obviously bad actions. Then go with the one that is the simplest/quickest or has the best gut feeling (feeling of rightness). React.

The main thing for me, is when I get that sense of urgency, all self-concerns and distracting thoughts fall away to the process above. It is a directed panic on the inside, but to the outside observer, it looks calm and methodological. When I get to the react part, it is all I concentrate on. Panic drops for something like intense focus.

I don't know if this will help, but maybe doing similar processes for little emergencies will train your reactions for larger ones.

"The Right Stuff" by Tom Wolfe has quite a bit on this topic. The answer seems to be habitualizing or "adapting out" fear. According to the book, when John Glenn was launched into space for the first time, the situation was so familiar that his heart rate held at around 70bpm.

I'm sure it can be helped, but I'm not sure if the kind of cool Neil Armstrong displayed can really be developed. If you want a good illustration of this, hang out with pilots and listen to their stories. I recall one pilot friend of mine, a flight instructor, describing an incident when he was guiding a student to landing in a small plane, when something malfunctioned and the plane started to tilt a hundred or so feet off the ground. My friend shouted "my plane" and took control, correctly diagnosed what had malfunctioned, and guided the plane to a safe landing.

Analyzing what happened afterwards, a few things were determined: first, given the altitude at which the malfunction occurred, my friend must have seen the problem, correctly diagnosed it, and acted in less than a second, and the total amount of time from when it offered until touchdown was something like four seconds. Second, this particular failure had occurred on this model of plane a handful of other times at such a low altitude, and had resulted in fatal crashes every other time.

So, being able to do that comes from a combination of a few things: tremendous rote training and knowledge of the plane, the ability to act calmly when your life is in peril, and an extremely efficient nervous system. Some of that can be developed, particularly the first one, and response to negative stimuli can probably be improved if you have time to think rationally, but in emergency circumstances like what an astronaut or a pilot go through, I have to say I think you're probably born that way, baby.

The best way I know of to deal situations that make you uncomfortable is to expose yourself to them, often but at low intesity, and build up a tolerance. Start small, and as you handle each issue, you'll find yourself thinking "I've got this, can't be much worse than [x] that I did last week."

I used to be a really heavy traveller, carry everything I could possibly need with me, just in case. I gradually whittled that down, and now when I get nervous about forgetting something when I pack, I just tell myself that so long as I have essentials (eg wallet, passport/ticket, change of clothes, netbook), I can fix everything else. So set yourself up with small stressful situations, know that you have a relatively painless way to back out of them, and talk yourself through it.

Have faith that you can fix whatever situation you find yourself in. You may have to start out by lying to yourself in saying that, but as you try (and succeed) you'll find that yes, you can handle things. Even the ones that really worry you.

The first way you deal with pressure is to know your shit. Risk is OK. This is really an importanct point, in addition to all of the very good other points made here (experience, etc).

Uncertainty = don't know what the f^ck is going on. Risk = these are the things that are going wrong, this is how it could get worse, this is how it could get better.

This makes it then a problem of managing information inbound/outbound, maintaining situational awareness (ie, your eyes and ears) and methodically making the best at what you've got to work with.

Very little bandwidth will be left over for "fear" or getting "nervous". On the Apollo mission, there is a story about 1202 (http://en.wikipedia.org/wiki/Jack_Garman), if you read this you will see how they handled it.

TL;DR The computer broke, and a split decision was needed to avoid a catastrophic failure.

Bales later recalled, "Quite frankly, Jack, who had these things memorized said, 'that's okay', before I could even remember which group it was in". His quick reactions and in depth knowledge led others on his team to give him the nickname "Gar-Flash".

This is a very good question. I have some experience with this; I find that as situations get more stressful, I become more and more calm and try to deal with it. I think it's a combination of a personality trait (my mother recently reminded me that I was the calmest of all her children) and a certain amount of self training. I used to remind myself (and others) that worry and panic do nothing to help the situation and that times of stress, more than ever, require a rational response. Eventually, the rational response mechanism discards emotional or stress based reactions as sub-optimal and you search for better ones. I know, easier said than done, but better said than never.

Neil Stephenson addresses this in his book, Anathem.

He states it's a fact "well known" within the military etc. that a certain percentage of folks respond very well to training for high risk, high intensity, high pressure situations (i.e facing live fire in combat) while a certain percentage simply flub and perform no better than someone who hadn't had the years of prior training.

Thing is, you don't know who's who until the event happens.

Anyway read the book it's really good in you're into this sort of idea, and into hackerish ideas in general