Night erections and daytime erections are affected by many factors, such as age, sleep quality, mental stress and so on. 1. Age: with the growth of age, the number and duration of daytime erections will gradually decrease, men in the 20-30 years old, energetic, strong desire, the number of daytime erections, after middle age will gradually reduce, more time is in the night when you go to sleep to have a married life. 2. Sleep quality: now young people are forced to live under pressure and work pressure, often stay up late to work overtime, resulting in mental depression during the day, the daytime erectile function becomes poor, in view of the daytime drudgery, it is easier to have sex at night when resting, so it is necessary to develop good sleep habits, improve sleep quality, to maintain the vitality of the male during the day. 3. Mental stress: due to the pressure of competition in social life, men often relax the mental pressure through night life, sex at night, resulting in low desire during the day, difficult to get an erection, at this time, you should adjust the mentality, stabilize emotions, but also regular exercise, enhance physical fitness, improve the symptoms of daytime without erection. As long as you can satisfy your personal sexual needs, it is not a big deal to have an erection at night but not during the day. If you suspect that you have a problem, you should go to a regular hospital in time so as not to miss your condition.