+1
KB...
I would say meditate and take deep breaths... but in reality after being engulfed with adrenaline, I haven't developed the biofeedback type of control to allow this to happen
read a book...
You don't need to go 2 the gym to workout. It's were you make it. There are tons of things you can do at home. I do jumping jacks, sit-ups, shadow boxing, bare crawls in the house, push-ups, jumping squats, and literally I have jogged at 2:30 am. Do whatever gets you tired. After a combination of those you should be tired.
Herbal anti-axiolytics. There are two that I can speak work well, one is called Happy Campers, the other is call Ex-Stress. Most Vitamin Shoppe's carry one or the other. If you can't get them immediately now you should keep some on hand for future need, seriously.
The best time to jog is at about 4am. Find a major road and run right down the middle of it. It will make you feel like you own it. Its hard to explain. Be out running while the world is sleeping..but about to wake up. On the way back home, you get to watch the sun rise and the sleepy heads driving to work.
As far as a natural remedy for calming down, prolly weed. It works well for most.
I usually drink wine and read a good book. That's what works for me.