Besetting sin humorous noun phrase
A particular weakness or bad feature
She was so deeply in love with him that she is blind to his besetting sin.
Impatience is my besetting sin.
Used to describe a situation in which people criticize and blame someone else for a fault, mistake or weakness that they also have themselves
The origin of this phrase is not clear.
What's going on?
A: What's shakin' bacon, man?
B: Yo, nothing much, and you?