Deep breathing is one of the easiest and most natural - yet most often overlooked - stress relief methods out there. Take in a deep breath through your nose, then exhale through your mouth, counting for about four seconds on each phase (in and out). Repeat this about 20 or 30 times.
When you start to breathe deeply on a regular basis, you'll notice how little you were actually breathing before, and how taking deep breathes, which increases oxygen levels in your body, is naturally calming