0 If you do not know when you are well off, you do not understand that your present situation is good compared with other people's or with what it might be like:
She's always complaining about her car - she doesn't know when she's well off (= she's lucky to have a car even if it's bad)!
NYA ORD
European
May 10, 2021
DAGENS ORD
Shimmer
know when you are well off