There are several mindful breathing techniques outlined in Buddhism and Thich Nhat Hanh does a beautiful job explaining them to us laypeople. He has also offered some different variations, including this well-known meditation:
“Breathing in, I calm myself. Breathing out, I smile.”
I recently came across a transcript of a dharma talk Thich Nhat Hanh gave on mindful breathing in 1998. I was struck by the way he described returning to our bodies and ourselves through breathing and meditation. Here’s a short excerpt:
“Breathing in, I am aware of my whole physical body; breathing out, I am aware of my whole physical body.”
That way, we start to recognize our whole physical body, we embrace it, and we are at peace with it. “Breathing in, I am aware of my whole body.” This seems to be very simple, but it is extremely important.... We are becoming one with our physical body. This is returning, coming back. We wandered a lot in the past, but now we are determined to come back to ourselves. The first destination is the breath, and then it is the body, and later the feelings, the perceptions, and consciousness, knowledge.
Take another step in order to come back to yourself as a physical body: “Breathing in, I am aware of my whole physical body.” This is already a love meditation. We have to be very interested in our physical body. “I recognize you, my physical body. I have abandoned you too much, but now I’m coming back, and I recognize you as existing.”
“Breathing in, I calm the activities of my physical body.” Because there has not been enough peace in your physical body, not enough harmony, there are wars in your physical body, sorrow, or pain; so you should be here for your physical body. “My physical body, I am here for you.” Take care, be interested in your physical body, and start to take care of your physical body. “I breathe in, and I calm my physical body.”
Read the whole talk here.