Doing that effectively requires you to know yourself, to think of a time when a work-related situation didn't turn out quite as you had hoped, and most important of all to not be afraid to admit failure. Maybe you paid too much attention to details that caused you to miss a deadline, or you rushed a project to make a deadline by skipping a couple of critical steps. Or maybe your over-aggressive sales tactics got the better of you and you lost a potential client.Everyone makes mistakes. A would be interviewer knows that, so don't pretend you've never failed. An interviewer is interested in seeing how you took responsibility for your failure, what you learned from it, and how you would prevent similar failures from happening again.If you can tell your story honestly and confidently, the interviewer may see someone who knows himself or herself well and is always looking to improve. That's something just about any employer would value in an employee.