The meaning of this sentence is: The same is true for the joy in the world. Since ancient times, everything has gone away like water flowing in the east.
From "Sleepwalking Tianmu's Song of Farewell" written by Li Bai of the Tang Dynasty
Excerpt from the original text:
The same is true for pleasure in the world. From ancient times, everything flows in the east. When will you return after leaving? Let's put the white deer among the green cliffs and ride to visit famous mountains as soon as possible. An Neng's ability to bend his eyebrows and bend his waist to serve the powerful makes me unhappy!
Translation:
The same is true for the happiness in the world. Since ancient times, everything has gone away like water flowing eastwards. I will tell you when I will come back. I will let the white deer graze among the green cliffs for the time being. When I go sightseeing, I will ride on it to visit the mountains of Mingchuan. How could I grovel and serve the powerful? This made me feel depressed and extremely uncomfortable!
Extended information:
This poem was written after Li Bai came out of the Imperial Academy. He wrote it in the fourth year of Tianbao (745) and in the fifth year of Tianbao (746). In the third year of Tianbao reign of Emperor Xuanzong of the Tang Dynasty (744), Li Bai was squeezed out by the powerful in Chang'an, was released from Beijing, and returned to his home in Donglu (in today's Shandong). Then embarked on a wandering journey again. This poem describing a dream trip to Tianmu Mountain was probably written when Li Bai was about to leave Donglu and travel south to Wuyue.
Li Bai had the ambition to help the world in his early years, but he did not bother to enter the official career through the imperial examination. Therefore, he traveled around the country and made friends with celebrities to build his reputation. In the first year of Tianbao (742) of Emperor Xuanzong of the Tang Dynasty, Li Bai's friend Taoist Wu Yun recommended Li Bai to Xuanzong, and Xuanzong summoned him to Chang'an. Li Bai had great hopes for this trip to Chang'an. In his farewell poem to his wife, "Farewell to the Expedition," he wrote: "If you wear the golden seal when you return, you will never see Su Qin not getting off the plane."?
When Li Bai first arrived in Chang'an, he was briefly proud. However, he was proud and refused to collude with the powerful. Because he offended the powerful and slandered his colleagues in the Hanlin Academy, even Xuanzong was dissatisfied with him. He only lived in Chang'an for more than a year before he was released with gold by Emperor Xuanzong of the Tang Dynasty. His dream of being a commoner and becoming a prime minister was completely shattered. This was a big political failure for Li Bai. After leaving Chang'an, he traveled to Liang, Song, Qi, and Lu with Du Fu and Gao Shi, and lived in Donglu's home for a period of time.
At this time, Donglu's home was quite large, and he could spend time at home enjoying himself and cultivating his character. But Li Bai didn't do this. He had an unstable soul and had higher and further pursuits, so he left his home in Donglu and embarked on a wandering journey again. This poem was written when he said goodbye to his friends in Donglu, so it was titled "Sleepwalking in Tianmu Mountain to Farewell the Dukes of Donglu".
Reference material: Sleepwalking in Tianmu’s Farewell - Baidu Encyclopedia