How to answer: Don’t be worried if they use the word “critical”. Maybe you haven’t made a bona fide “critical” mistake. You can instead tell about a time you had a “near-miss” but prevented an error by asking someone to double check you, or by listening to your inner voice. Be sure and have your example ready and include the event, what steps you took, and what you learned. Frame it as a learning experience you are grateful to have had.