Tonglen meditation practice means "taking in and sending out." In Start Where You Are, Buddhist nun Pema Chödrön describes it as a way to "let ourselves feel what it is to be human" and by doing so to "widen our circle of compassion." In the first stage of the practice, you rest in a state of openness or stillness. In the second, you work with texture through breath awareness, visualizing that you are breathing in dark, heavy, and hot (claustrophobia or fixation) and breathing out white, light, and cool (spaciousness, freshness) through every pore in your body.
The third stage works with a specific instance that you are aware of. You breathe in the pain of a person, animal, or a distress you are personally feeling, and you breathe out something to relieve the pain — a good meal, kindness, confidence.
In the fourth stage, you breathe in the pain of all those suffering like the one you have just cared for — all hungry people, all hurting animals in the world, all those feeling inadequate. You breathe out whatever will lighten their load. Chödrön advises always working both with the immediate suffering of one being and with universal suffering of all. In this way, your practice is both heartfelt and visionary.— Frederic and Mary Ann Brussat in Spiritual Rx: Prescriptions for Living a Meaningful Life