Mr. Zongxuan's Xuan Gang Lun: Chapter 22 - Emptying the Will with Whiteness
The spiritual soul loves purity, while the corpse soul loves filth. If one constantly strives to empty and whiten their will, and cleanse their form like snow, then the spiritual soul will be joyful and healthy, and the corpse soul will be refined and extinguished. One whose spirit is healthy and corpse is extinguished becomes increasingly clear and fresh. Even without light ascension, I would certainly call them an immortal. Furthermore, those who feel sorrow and resentment are companions of Yin. Those who are joyful and content are companions of Yang. Thus, when the heart is sad, Yin gathers; when the will is joyful, Yang disperses. Those who are neither sad nor joyful, living in tranquility and non-action, are called 'Yuanhe' (Primordial Harmony). Without Yuanhe, one cannot attain the Dao.
Explanation: The spiritual soul loves cleanliness, while the corpse soul loves dirt and disorder. If one frequently maintains a state of desirelessness, cleansing oneself as if with pure water, the spiritual soul will be at peace, and the corpse soul will be refined away. When the spirit is healthy and the corpse is extinguished, one becomes increasingly clear and fresh. Although this may not lead to flight into the heavens, one must still be able to become an immortal. Furthermore, those who frequently feel sorrowful and sentimental are in resonance with Yin energy, while those who are often happy and joyful are in resonance with Yang energy. If the heart is sad, Yin gathers; if one is often joyful, Yang disperses. Only by being neither sad nor joyful, and practicing tranquility and non-action, can one be called 'Yuanhe'. Without achieving Yuanhe, one cannot be considered to be cultivating the Dao.
Analysis: Modern research suggests that if people are frequently unhappy, they may develop depression, which is caused by the gathering of Yin, while being often happy can lead to longevity. This is the most common view. However, research by Andrew Steptoe, a psychologist and epidemiologist at University College London, indicates that scientists have realized such results are inaccurate.
The English Longitudinal Study of Ageing aimed to obtain more precise data. This project has tracked over 11,000 people aged 50 and older since 2002. In 2004, approximately 4,700 participants provided four saliva samples in one day and simultaneously assessed their emotional states (happy, excited, satisfied, worried, anxious, and afraid). Among the 924 elderly individuals who reported the lowest emotional states, 7.3%, or 67 people, passed away within five years. Among those who reported the best emotional states, this rate was nearly half as low, at 3.6%, meaning 50 out of 1,399 people. Steptoe stated that the research shows a correlation between good emotions and longevity, but it does not prove that happiness makes people live longer.
In simple terms, current research conclusions suggest that bad moods indeed significantly increase the risk of death. Simultaneously, from a psychological perspective, people with long-term suppressed moods are more likely to develop mental illnesses, which is the result of the 'gathering with Yin' referred to in the Xuan Gang Lun.
Although there is currently no more evidence showing that joy affects lifespan, excessive excitement does affect human health, which is a fact. This is because the enhanced excitation of the sympathetic nervous system is one of the important mechanisms for the occurrence and development of many cardiovascular diseases, including hypertension, which is the result of Yang dispersing.
Therefore, a more orthodox view should understand that neither excessive sorrow nor excessive joy is the correct path of cultivation. One should remain unshaken by worldly affairs, without sorrow or joy, practicing tranquility and non-action; this is the way of cultivation.