Yes, we all automatically breathe but what we often don't pay attention to is how we breathe. If we're stressed or anxious most often our breath will be more shallow and quick.
A great way to relieve stress is to focus on slow deep breaths, when you inhale allow your abdomen to expand fully as far as it will comfortably go so that you are fully filling your diaphragm, then slowly exhale gently pushing your abdomen in as far as it will go so as to empty the diaphragm. You can place your hand/s on your abdomen for the first few attempts to help get the feel of it. Repeat this breathing action approx 10 times or until you feel calmer and more relaxed.