It means let us cherish the present moment.
The original sentence is I asked Qingshan how old I will be, and Qingshan asked me when I will be free. People have no leisure in middle age, and I fear seeing Qingshan in old age.
Relevant poems include: People in middle age have no time to relax, and they are afraid of old age when they see the green mountains again. When the mountains are green, you are not idle. When you are idle, sleep with the mountains. I asked Qingshan how old he was, and Qingshan asked me when I was free. I am not idle as long as the mountains are green, I am busy all my life just for money. After going around and around for decades, the loess reaches my chest in the blink of an eye. I laugh at the green mountains, my face remains unchanged, and the green mountains laugh at my old age. Like an ox, it has no time to rest when it gets old. If it does, it will sleep in the mountains. You need to cherish every fate in life, and don't wait for your children and grandchildren to stand in front of their graves.