One of the four Viharas. I practise this once a day. I do not have a fixed time period, as soon as I feel calm and silence, I wake up.
Close your eyes. With every exhalation, allow the feeling of compassion to radiate from your heart, filling the space around you with the energy of compassion. Inhaling compassion, allow it to fill your heart and every cell of your being, and then when you exhale, let compassion flow forth to all beings who are in any way suffering, and fill the world around you with empathy and compassion. Visualize an ever-expanding sphere of light radiating from your heart, filling the entire world with compassion, and embracing all living beings in the loving light of universal compassion. See compassion encircling the earth for everyone. Allow yourself to send this feeling of compassion also to yourself, a sense of caring and patience and understanding for yourself, nourishing yourself and being loyal to the truth within yourself. Breathing compassion, become compassion, and being the living embodiment of compassion, allow this feeling to radiate from you as you shine the light of compassion, filling the world with the light of compassion.