There is something in the poem of children's grandmother: life is like a dream. . . What's behind?

Life is like a fog and a dream, and life and death are at ease.

This poem is from Zhuangzi's Happy Travel. The whole poem is as follows: life is like fog, but it is like a dream. It is comfortable to talk about life. Yun Qi's dark clouds have cleared, his heart is red, and his heart is red. The maple dance is cold, and the royal sword is free. Drunk singers laugh with you, and there is no winning move in the sword. Ten years, a sword in the world, there are documents coming from all directions. Who rises in Dong Fangbubai, I am the only way. Pity the long water in my hometown and love the stormy building at dusk. Huanxiang has more tears than hate, far away. If the heart regrets breaking the moon, the sky is deeply hesitant. Qian Wen's marriage is short-lived, which opens the world of mortals. Liu Xingguang is boundless, and the wind recalls lonely dreams. It's a long way to go, Xiu Yuan. I love you, the sooner the better. Once I tasted the vast sea, I felt that the water in other places was pale; Once you have experienced the clouds in Wushan, you feel that the clouds elsewhere are eclipsed. Hurried through the flowers, lazy to look back; This reason is partly because of the ascetic monk, and partly because of who you used to be. Love seems to rush to the morning dew, leaving the past to laugh at the east wind alone.