Courtesy of the inspiring Mary Jaksch, this has got to be the simplest technique of all. Walk to a window, look outside, as far into the distance as you can and take one single, slow, deep breath. That's it! If you think it's too simple to bother with, I challenge you to try it for a day or two and feel for yourself just how much it can steady and calm your mind.
You could try this several times a day, using any window you see as a cue to stop for a second or two, drop your shoulders, and breathe. Be fully aware of your breath, feel it enter and leave your lungs and allow yourself to feel how it calms you for that one moment of reflective pause.
Related Posts & Resources You Might Enjoy:
A Simple Guide to Mindfulness Meditation on Good Life Zen
Pranayama: Breathing to Calm your Mind and Heal Your Body on Living by Design
Your Breath as Medicine on Living by Design