Recognise the stress you hold in your body

When we are stressed, the muscles in our body react accordingly. While not a long term solution, recognising where in your body you are holding stress, can be helpful for momentary de-stressing.
To do this, sit down with your back fully supported. Close your eyes and take a few deep breaths. Then do a slow body scan from the top of your head, down to your toes. Notice which parts of your body feel tense. As you observe that, take a moment, clench that muscle as tight as you can, and then relax it.