Emotional distress catalyzes physiological stress.

Beliefs alter physiology to the degree to which we are fused with them. For example, the thought This headache could be a brain tumor could create enormous emotional distress, leading to physiological stress and illness. The ability to step back from that thought and take it lightly causes no distress and is harmless. The most evidence-based method for learning to take our thoughts lightly is mindfulness practice, such as Zen, Vipassana, or MBSR.  Mindfulness-based psychotherapy, such as Acceptance and Commitment Therapy (ACT) has also proven efficacious. These practices develop environmental mastery, which dramatically reduces emotional/mental stress, thereby improving quality of life and health.