In this case, essence may mean sperm, urine, or the finest essence of water and grains in chronic diarrhea. Yi Zhi Ren's second main use is in Chinese medical psychiatry and the treatment of dementia, whether pervasive developmental, senile, or the sequela of drug abuse, impaired memory, and difficulty concentrating, as in attention deficit-hyperactivity disorder. Thus, this medicinal seems to have certain empirically specific effects on the capacity to think and remember. Both formulas quiet the spirit by constructing and nourishing the spirit. I believe this quote nicely underscores the relationship between the so-called five spirits in Chinese medicine and especially the relationship between thought and the mind or will.
Intention is the dynamic of the heart spirit.
It stirs but is said to have no form. Will is the concentration of intention. Thought is the change and stirring of will. Worry is what is called thought which has planned remotely. Readers should not be perplexed by this.