It is merely 3:30 am now, but I woke up. I went to bed at 11 pm last night. It was not so early. In recent years, my sleep has always been in this kind of situation: go to sleep later and wake up in the middle of the night. After a while, I fell asleep again, and then woke up again. Fall asleep and wake up two or three times during one night. It may be troublesome for someone else to have this kind of sleep, but for me, it doesn't matter because I can take advantage of it efficiently. When I wake up, I write paragraphs in English. When I am sleepy, I just go to sleep again. I never feel bored when I wake up in the middle of the night, because I have positive things to do and I am always afraid that I don't have enough time to do them.