I have a routine I follow when I know that things are about to get ... dynamic.
I take a slow breath through my nose until my lungs are full down past my belly -- and a little more -- and hold it for a slow count of five. Then I let it out slowly through my nose until my lungs are empty. Repeat twice more.
When I was taught this, I was told that it would help me shoot more accurately, hit harder and think clearer.
While I can't prove that -- and have no real desire to find out -- I'm of the impression that when I have time for this I don't get tunnel vision; the adrenaline shakes aren't as bad, and -- most importantly -- when I breathe like this the panic monster stays shackled.
As a Pavlovian side-effect of doing this before hopping off of choppers, going through doors, climbing into rings, and other assorted adrenaline-events is that when I do the breathing ritual, my body seems to start dumping endorphins pretty much immediately.
I have discovered that this comes in handy when I'm knackered. I do the breathing and it's like a double-shot of espresso -- the world clears and I can focus on whatever needs doing.
This has gotten me through more than one 72- or 96- hour ARTEP, but I've slept for a day or two afterwards.
One of the things that disturbs me the worst about this pericarditis episode is the fact that I'm only good for about four hours, then I'm exhausted.
Well, today Herself, AEPilotJim and I went out to do some errands for the upcoming PhlegmPhest and I hit my four-hour limit. Not even really thinking about it, I took a deep breath, held it, let it out; lather, rinse, repeat X2.
I was myself! I was awake! I had energy!
For about twelve minutes. Then I augered-in, we got home, and I slept for two hours. And I'm still wiped-out.
Yeah. We won't be doing that again for a while.