As obvious and simplistic as it may seem, I've come to really discover the power of just BREATHING. I stop whatever I'm doing and breathe in, slowly through my nose... then breathe out of my mouth, twice as slowly...... and continue the cycle a few times. If you don't feel it working, just keep doing it a bit longer. Take your time just doing nothing else but breathing; paying attention to how it feels physically in your body to breathe, in, and out.

If you have more time, and somewhere to relax, you can do progressive muscle tension and relaxation exercises. Stretch your arms out, tense them as much as you possibly can, making them tighter and tighter as you count to 7...... then relax totally, shaking them out a bit... noticing how those muscles feel when they're let go and relaxed. Do the same with your legs, feet, chest, face, etc. Sometimes I just do one full body tense, and then relax. It really helps with insomnia.