Welcome to English in a Minute, where we teach you all about idioms in American English.
Sometimes being truthful is hard, especially when you have to tell a person something unpleasant.
There is a phrase in American English that is used for this purpose.
A: I just can't believe her. She said that I look sloppy and bad and that my clothes don't fit well. She said that I look like I live in a garbage can.
B: Well, if the shoe fits, wear it.
If someone says to you "if the shoe fits, wear it." they're saying that if something applies to you then you should accept it. It can be unkind to say. So you should use this phrase only with people you kown very well.
And that's English in a Minute.