江河日下

话说唐朝时期，有一个名叫李白的诗人，他年轻的时候才华横溢，诗作惊艳天下，名满长安。可是后来，他沉迷酒色，不思进取，渐渐地荒废了学业，才华也日渐衰退。曾经的知己好友也渐渐疏远了他，他的生活也变得越来越糟糕。原本充满朝气蓬勃的他，最终落得个孤苦伶仃的下场，正如江河日下，不可挽回。

huashuo tangchao shiqi, you yige mingjiao li bai de shiren, ta nianqing de shihou caihua hengyi, shizuo jingyan tianxia, mingman changan. keshi houlai, ta chenmi jius, bus jinqu, jianjian de huanfeile xueye, caihua ye rijian shuai tui. cengjing de zhiji haoyou ye jianjian shuyuanle ta, ta de shenghuo ye biande yuelaiyue zaogao. yuanben chongman chaoqi pengbo de ta, zhongyu luode ge guku lingding de xiachang, zhuru jianghe rixia, buke wanhui.

In the Tang Dynasty, there was a poet named Li Bai. In his youth, he was exceptionally talented, his poems stunning the world and making him famous in Chang'an. But later, he became addicted to alcohol and indulgence, neglected his studies, and his talent gradually declined. Former close friends drifted away, and his life became increasingly miserable. The once vibrant man eventually ended up lonely and abandoned, just like a river flowing downwards, irreversible.

常用作谓语、宾语、定语；形容事物逐渐衰败、每况愈下。

changyong zuo weiyua, binyu, dingyu; xingrong shiwu zhujian shuibai, meikuang yuxia

It's often used as a predicate, object, or attributive; to describe things gradually decaying and getting worse and worse.