How do you cope with stress in IT?

I work in a fast pace IT workplace. I'm a UNIX admin for several hundred trading systems, we're essentially a stock exchange. We deal with hundreds of millions of pounds a day, 4 second downtime could cost a few million easily. My colleague is out for 2 weeks vacation so it's down to me to keep our European operations running. When there's two of us it's great as we can fall on each other for support. But when I'm on my own sometimes I realize I'm running the operation singlehanded and the stress gets to me. Stomach cramps, loss of appetite etc. How do you guys cope in these situations? I've been here two years and I still get stressed when I'm working on my own. I don't eat poorly and I try to exercise regularly outside of work. How is it for programmers, testers and other sys admins out there?