In addition, there is a poem about Du Fu's tears all his life, from youth to middle age, which shows that it is not easy for an ordinary person to live, that is, he is now 50 and only has a few lines to sit and lie down.
This sentence describes my present situation after middle age. I am old and weak, so I can't move easily. Therefore, I sit and lie more, but stand less. One sentence changes time and space from fifteen to fifty at once. It's an unspeakable vicissitudes.