Summer controls fire and the heart is the organ of fire which governs emotions. Thus, the summer-heat easily acts upon the heart to cause uprising of the heart fire, giving rise to restlessness of the mind, irascibility, anxiety, uneasiness, even insomnia, etc. Particularly, old people have the poor ability to endure the climatic variations. They are often in an anxious state of mind. This affects their health, even induces diseases. Accordingly, in summer emotional regulation, people should tranquilize the mind, treat people and deal with things calmly, avoid anger and vexation so as to cultivate temperament in a quiet state. Some classics repeatedly mention that in summer people should "cultivate the temperament peacefully and avoid being restless in the mind" and "Cultivation of temperament is more important than health preservation", etc. Only in this way can people conform to the principle of summer health preservation.
