Deep breathing
A simple way to help manage your stress is to consciously use deep breathing. When we get stressed we tend to take more shallow breaths, which leads to lower oxygen, which then reinforces a feeling of stress. To overcome this either sit up straight in a chair or lie down so that you can fully expand your lungs, then slowly breathe in as deeply as you can, hold it all in for a count of 2, and slowly breathe out. Repeat twice, or until you are feeling better and calmer.
This is something that you can do anywhere and you can make time for no matter how busy you are.