There are many reasons: 1, and everyone around you is like this. You want to go to bed early with the public, but the dormitory lights are turned off very late and the roommate's voice is very noisy. You will be late for college, and you are all sleepy. I can't bear to sleep at night, play games, brush my space, brush my circle of friends and brush my Weibo. Before I know it, it will be very late. 3. You usually play hi, critical moment. . . Anyway, as far as my experience is concerned, I usually sleep at home at 9: 00 in junior high school, at 11: 00 in senior high school, around 12: 00 in college, and basically at 1: 00 for graduate students. I guess I'll go to bed after work at two or three. . . I always want to go to bed early, but I just can't. People around me are also like this, complaining about lack of sleep, but still staying up late. . .