in Chinese medicine, Anger is one of the worst emotional toxins in the body. Anger is associated with the wood phase, and so is the liver. The virtuous behavior of the liver is Ren 仁, benevolence or compassion. When we practice, the real Qigong is the development of benevolence, the compassionate heart. The reason this brings health is that benevolence/compassion develops liver/wood, which is the spring, the birth of all life. It dissolves anger, and anger is what cuts off spring (i.e. it cuts off life itself). Back to Confucius:
人不知而不慍,不亦君子乎。Others do not understand, and yet he feels no anger. Is this indeed not a perfected sage? (Analects, Book 1)
Henry