BMO wants to hear that you don't hide or ignore your mistakes. They are a company that knows how to improve and grow based on learning from past failures. How do you think they have been so successful?! Of course, it's difficult to come up with a good example, but you can do it if you plan ahead! This is where interview preparation is key! Just remember, the interviewer isn't worried about whether you will fail again. They're not looking for faults. The interviewer really just wants to find out how you will handle failure since it is sometimes unavoidable! Think about a situation that occurred, at work, school or when volunteering that you regret. What do you wish you could have done differently? Think about what you learned. Another way to think about this question is to reflect on your greatest learning experience! Sometimes bad planning can get us into emergency situations, like not looking at a map and getting horribly lost in the middle of nowhere, or not studying for a test that we thought would be much easier than expected! Keep it simple, and focus on how you grew from the experience!