if the cap fits

if the cap fits(, wear it)

If something (typically negative) applies to one, one should acknowledge it or accept responsibility or blame for it. I know you don't like being called unreliable, but if the cap fits, wear it. A: "Why do teachers always treat me like some kind of troublemaker?" B: "If the cap fits...."
See also: cap, if, wear
Farlex Dictionary of Idioms.

if the shoe fits, wear it

Also, if the cap fits, wear it. If something applies to you, accept it, as in These problems are hard to solve, and most people would need help, so if the shoe fits, wear it! This expression originated as if the cap fits, which alluded to a fool's cap and dates from the early 1700s. Although this version has not died out entirely, shoe today is more common and probably gained currency through the Cinderella fairy tale, in which the prince sought her out by means of the slipper she lost at the ball.
See also: if, shoe, wear
The American Heritage® Dictionary of Idioms by Christine Ammer.

if the cap fits

or

if the cap fits, wear it

BRITISH
You say if the cap fits or if the cap fits, wear it when you are telling someone that an unpleasant remark which has been made about them is probably true or fair. `She seemed to be suggesting I was lazy.' — `Well, if the cap fits.'
See also: cap, fit, if
Collins COBUILD Idioms Dictionary, 3rd ed.

if the cap fits (, wear it)

(British English) (American English if the shoe fits (, wear it)) (saying) if a person feels that a critical remark applies to them, then it does: ‘There are too many lazy people in this house.’ ‘Including me, I suppose?’ ‘If the cap fits, wear it.’
See also: cap, fit, if
Farlex Partner Idioms Dictionary

If the shoe fits, wear it

and ITSFWI
sent. & comp. abb. If this applies to you, do something about it. Maybe this applies to you. ITSFWI.
See also: if, shoe, wear
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions

if the shoe fits, wear it

If something applies to you, accept it. This expression is a version of an older term, if the cap fits, put it on, which originally meant a fool’s cap and dates from the early eighteenth century. This version is rarely heard today. Its replacement by a shoe probably came about owing to the increased popularity of the Cinderella story, and indeed, an early appearance in print, in Clyde Fitch’s play The Climbers (1901), states, “If the slipper fits.”
See also: if, shoe, wear
The Dictionary of Clichés by Christine Ammer
See also:
  • (one) could use (something)
  • drive (one) out of office
  • force (one) out of office
  • force out of office
  • give (one) (one's) head
  • give head
  • give somebody their head
  • give someone their head
  • cooking for one
  • as one door closes, another one opens