1. It stimulates feelings of gratitude
  2. It stimulates the secretion good body chemicals, which reduces the impact of stress on the body
  3. It stimulates the brain to respond in a healthy and beneficial way

See Richard E. Boyatzis, Melvin L. Smith and Nancy Blaize, “Developing Sustainable Leaders through Coaching and Compassion,” Academy of Management Learning & Education, Vol. 5, No. 1 (Mar., 2006), pp. 8-24.