I'm Jewish. We yell. We're loud. It's just who we are. But in my mother's warped world, she calls it "healthy yelling."
Sure, we want to remain calm and quiet and controlled, and we don't have to yell about everything, but it's okay to yell periodically, as long as it doesn't become abusive or your only method of communication. A few quiet words from my dad saying, "You know, you really hurt your mother," can be more powerful than any of my mother's rants. Do I yell at my kids? Yes. But more often, I talk to them calmly and tell them, if they don't listen and move from the computer, the TV, the Wii, or whatever, they lose the privilege. It works.
Children don't have to grow up thinking everything they do deserves an award, a medal, a trophy. You don't have to be perfect all the time, and life does get messy. That's when you may end up yelling. Pick your battles and don't become abusive. The rest of the time, step back for a moment and find a healthy way to communicate.