以史为鉴

don't forget past events, they can guide you in future (idiom); benefit from past experience

to learn a lesson from the mistakes of one's predecessor (idiom)

to review the old and know the new (idiom, from the Analects); to recall the past to understand the future

to review the old and know the new (idiom, from the Analects); to recall the past to understand the future

to take sth as a warning (idiom); to draw a lesson from a case where things turned out badly

to observe the past to foresee the future (idiom, taken loosely from Book of Songs); studying ancient wisdom gives insight into what is to come