有则改之，无则加勉

yǒu zé gǎi zhī , wú zé jiā miǎn

Definitions

1. correct any mistakes you made, but maintain your good record if you did not make them (idiom)

(possessive particle, literary equivalent of 的[de])

(literary) (conjunction used to express contrast with a previous clause) but; then

to add

to change

to have; there is

not to have

to exhort