The definition of shoot oneself in the foot is:
(idiom) make a situation worse for oneself by accident
A: Did you meet your new girlfriend’s parents last night?
B: Yes I did.
A: How did it go?
B: I shot myself in the foot when I told her father I was unemployed and lived with my parents.
When Michelle got drunk before her final exam, she was shooting herself in the foot. She failed the test!
During the job interview, Annie managed to shoot herself in the foot when she told the interviewer that she was lazy and often late for work. She didn’t get the job.
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