前车之覆，后车之鉴
qián​chē​zhī​fù​hòu​chē​zhī​jiàn

to learn from past mistakes

前车之覆，后车之鉴 前車之覆，後車之鑒 qián​chē​zhī​fù​hòu​chē​zhī​jiàn
to learn from past mistakes
lit. the cart in front overturns, providing a warning to the cart behind; fig. to draw lessons from the failures of those who came before or from one's own past mistakes