The importance of state of mind in treating cancer is reflected in the following aspects: First, cancer is closely related to hereditary factors, physical and chemical factors, as well as bacterial and viral infections and mental factors, etc., in which mental factors play a very important role for cancer patients, and a good state of mind is also a key factor in treating cancer patients. Secondly, due to mental tension, psychological pressure, fear and depression, patients’ immunity is low and their psychological reaction is strong, which directly damages the central nervous system and can cause endocrine function disorder as well as vegetative nerve function disorder and dysfunction, etc., so that the stress and immune function of the organism is inhibited, which leads to rapid proliferation and accelerated growth of tumor cells, thus causing tumor metastasis and proliferation, e.g. patients with lung cancer and liver cancer show more obvious symptoms, and patients with lung cancer and liver cancer show more obvious symptoms. For example, patients with lung cancer and liver cancer have more obvious performance. Thirdly, due to mental stress, patients suffer from insomnia, weakened immune function of the organism and decreased ability to resist diseases, which will lower T lymphocytes and B lymphocytes, thus decreasing the ability of the organism to resist the attack of diseases. Fourthly, when the organism is under continuous stress or depression, the body will produce the stress hormone adrenaline. When the cancer cells are exposed to the adrenaline environment, the anti-cancer proteins will be inactive and cannot kill the cancer cells normally, thus accelerating the development of the cancer and decreasing the effectiveness of the anti-cancer treatment. Therefore, it is suggested that patients must keep a good mindset, face the condition positively and cooperate with clinical treatment, and they will surely battle the disease.