Well, it's a fact that exercise helps you reduce your stress. When people are fighting or are pissed off about something, they tend to be physical about it; to work off that negative energy. Whether it be just something simple like a walk around the block, or more intense, a run for example, exercising can make you feel a lot better. Just something about it clears your head; not to mention the adrenaline rush if you're working hard enough.
I find for me, regular workouts really help me relax; give my brain a rest for a few hours a day and just focus on lifting, or running, etc. Now, my definition of regular is probably a little out of whack compared to other's. Take, for example, tonight. I had some things that I was stressed about and just generally frustrated; you know the kind. So off to the gym I went, with nothing more in my head than to work my a** off. I started off with the stair master, one of my favorite machines for really getting the intensity up. I went on that for an hour, at a high level(15). Usually at this point, I would call it a night, stretch, and go home, yet I didn't feel like sitting at home. I knew once I got back, I would still be active and start thinking about all the emotional problems in my life right now. Just to push myself even more then, I went on the stationary bike; just ten minutes I told myself. Well, I ended going for half an hour, just getting drenched in the process. By the time I was done that, I could hardly stand up, let alone think of anything besides the basic; one foot in front of the other, all the way to the showers.
Now, cardio is great for that, but I would prefer lifting. When you are lifting weights, you are more or less forced to concentrate and not think of anything else. When I'm doing a heavy lift and let my mind wander, I'm risking losing focus and hurting myself. So you see, I simply can't let anything else occupy my mind at that time. For example, if I'm doing squats and have literally hundreds of pounds on my shoulders, if I lose focus and make a mistake, it could be a fatal one. Just think about it, you have four or five hundred pounds of dead weight across your shoulders and upper back, and you lose your balance because you're not focused. The bar will come crashing down, all that weight falling on your back. Can you say broken neck? When I am doing heavy squats, I am totally focused on the exercise; in fact, if you were standing right next to me talking away, I wouldn't even hear you. It's one of those rare moments when your mind is clear of all other thoughts except for one; getting that weight back to the pins so that you can end that torment to your legs:P.
There are many other ways of getting rid of stress of course, but I find for me, working my butt off until I can't think of anything else is the best way; plus it keeps me in good shape!