前事不忘， 后事之师

前事不忘， 后事之师 [qián shì bú wàng hòu shì zhī shī]

1. ■ The past is the prologue.; By not forgetting past events, one can draw lessons from them.; Past experience, if not forgotten, is a guide for the future.; The past not forgotten is a guide for the future.; The remembrance of the deeds of past ages is the best guide in the future.; You can draw lessons from the past if you don't forget it.