If you have a good erection at night but poor erection hardness during sex, it may be caused by psychological factors, neurological factors, endocrine factors, vascular factors and other reasons. 1. Psychological factors: If the patient has depression, anxiety or too much pressure, it is easy to affect the hardness of erection during sex. 2. Neurological factors: Since penile erection is a neurovascular activity, if there are problems with the relevant nerves, such as damage to the penile corpus cavernosum, the brain and other nerves, the hardness of the erection will not be enough during sex. 3. Endocrine factors: men with thyroid disease, hypogonadism, adrenal gland lesions and diabetes, etc., will have an impact on the hardness of erection during sex. 4. Vascular factors: the presence of heart disease, high blood pressure and arteriosclerosis and other cardiovascular diseases, it is easy to reduce the blood flow to the penis, in the sex life will affect the hardness of the penis erection. There are many other reasons for this situation, it is recommended that patients go to a regular hospital to do a detailed examination, through the doctor’s professional judgment, to identify the specific causes, and then give reasonable treatment.