Under the trees into the valley
It is an idiom, which refers to abandoning the light from the dark, or from a good situation to a bad situation. It comes from Mencius Teng Wengong.
From the high tree down, into the deep pit valley.
Source of "Mencius Teng Wen Gong Shang": "I heard that it came from the valley, and moved to the arbor, but I didn't hear that it came from the arbor and entered the valley."
Under the trees into the valley
to compose poems while holding the lance horizontally in the saddle - héng shuò fù shī