10 second tense and relax technique
This is a very simple and effective 10 second technique:
Step 1: Tense all your muscles, screw up your eyes and face, as you slowly breathe in.
Step 2: Hold it for 1-2 seconds at your maximum in-breath. Increase the tension in your face and body as much as you can.
Step 3: Breathe out, let go, open your eyes and relax all your muscles.
That should feel good.
As with most relaxation techniques, use this often to get the best results.