Yuan Zhen (779–831) was a famous poet, novelist, and politician from Tang Dynasty. This is the most famous one of a set of five Remembrance in Separation (离思) poems, which were all written in memory of his beloved wife who unfortunately passed away from illness after seven years of marriage.
Consider no waters seen have I Tsang Sea*,
曾经沧海难为水，
Be not any cloud but the cloud at Wu Peak**.
除却巫山不是云。
Care not to linger, slipping by the flowers,
取次花丛懒回顾，
Partly Tao I seek and partly be for thee.
半缘修道半缘君。
* The Tsang Sea is the ancient name for the East China Sea. It also sometimes refers to the sea or ocean in general. Here Yuan Zhen was quoting Mencius (372–289BC), who once said that it was difficult for people who had seen the ocean to consider any other waters.
** The Wu Mountain is known for the wildly changing sea of clouds. Song Yu (298–263BC), a poet from the Kingdom of Chu, once told the story of King Huai of Chu and the Goddess of the Wu Mountain. When King Huai was visiting Gaotang Temple at the Wu Mountain, he felt tired and took a nap. He dreamed of a lady who said that she was the Goddess of the Wu Mountain; she heard that the King was visiting and wanted to offer him her bed and pillow. The King thus lay down with her. Before she left, she said, “I live at the southern peak of the mountain. In the morning I am the colorful morning clouds, in the evening I am the drizzling rain. Every morning and night, I am just below the balcony.” The next morning the King looked outside and found the view as described, so he built her a temple, calling it Morning Clouds.