When a mother is trying console an upset child, she will lower her voice and talk in a slow, calm manner. This works because people tend to adopt the attitudes of the people around them. If you are interacting with someone who is stressed out, they will be radiating a lot of nervous energy, which will probably make you start felling stressed out as well. Conversely, if you hang out with people who are calm and relaxed you will start feeling more calm and relaxed as well.
If you are feeling stressed out, you can use this technique to get rid of some of that nervous energy. First, make sure that you are
breathing properly. Now, slow everything down in an exaggerated way. Speak slowly, walk slowly, move your arms slowly, breath slowly. Pretend that someone has hit the slow-motion button on the remote control for your life. It may seem unnatural or silly, but try to do this for at least 10 minutes and you may find that you have slowed your mind down and that you feel a lot more relaxed.