Meaning of the word "a friend's eye is a good mirror" in English

What does "a friend's eye is a good mirror" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

a friend's eye is a good mirror

US /ə frɛndz aɪ ɪz ə gʊd ˈmɪrər/
UK /ə frɛndz aɪ ɪz ə gʊd ˈmɪrə/
"a friend's eye is a good mirror" picture

Idiom

a true friend will tell you the truth about yourself, helping you see your faults and virtues clearly

Example:
I didn't realize I was being so rude until Sarah pointed it out; truly, a friend's eye is a good mirror.
You can always trust his critique because a friend's eye is a good mirror.