不知进退

Cited in Hong Mai's Song-dynasty 《容斋续笔》: Murong Shaozong, despite winning a major battle against Hou Jing, then besieged Yingchuan 'not knowing when to advance or retreat' (不知进退) and ultimately drowned. The idiom captures that fatal failure of judgement.

usage

Can describe both speech and action - saying things one shouldn't, or pressing on/holding back at the wrong moment. Often paired with 不识时务 bùshí shíwù (out of touch with the times).