In order to lead to peace of mind, we will consider the mechanism by which human emotions are generated and the mechanism by which neurotransmitters are used to store memories. We will examine the mechanism by which feelings of fear and joy are generated, which are important for safety (protecting the body) and peace of mind (maintaining peace of mind). Humans perceive the environment and events through their sense organs, and the stimuli are transmitted to the brain. Fear responds to the amygdala, and joy responds to the nucleus accumbens, which generates neurotransmitters (noradrenaline, dopamine) and transmits them to neurons in the brain. I know what happened.