前车之覆，后车之鉴

lit. warning to the following cart (idiom); don't follow the track of an overturned cart; fig. draw lesson from the failure of one's predecessor

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

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

lit. to follow in the tracks of an overturned cart (idiom); fig. to follow a path that led to failure in the past

lit. to punish those before to prevent those after (idiom); to criticize former mistakes firmly to prevent them happening again

Fall into the moat and you'll be wiser next time (idiom); One only learns from one's mistakes.