Long-term stress at work and school, incompatibility of interpersonal relationships at work and at home, and major misfortunes in life are three important factors in causing cancer. Clinically, most breast cancer patients have more or less bad emotional problems, and between six months and eight years before the onset of the disease, they often experienced the blow of major life events, such as the death of a close relative, marriage change, and layoff. Poor emotion is also an important reason for the development of breast cancer. To ensure breast safety, it is necessary to have to maintain a healthy state of mind first. Human emotions are always affected by the surrounding environment and events, and emotions can affect one’s immune system. Good emotions can improve the ability of human organs to coordinate and resist diseases, while bad emotions can induce organ dysfunction and lower the immunity of human body, and cancer cells will take advantage of the situation. This is also the reason for the saying “all diseases originate from the heart”. Negative emotions can increase the secretion of lactin, which may lead to breast cancer. Therefore, among breast cancer patients, there are more urban than rural women and more intellectual women than professional women. Even in the treatment stage of breast cancer, if the breast is removed, it often brings a huge psychological shock to breast cancer patients, which results in a series of psychological problems. Patients with cheerful personality tend to have good treatment effect, while those with high mental stress tend to have poor treatment effect. Therefore, whether it is prevention or treatment, we should get rid of depression, adjust our mind and maintain good living habits as an important means to prevent and treat breast cancer.