I would suggest interviewees to maintain their cool and not to over react. Just think that your life is not going to end if you do not clear this interview. There is always a next time where you can prove yourself and get selected. The interviewer asks this question to see how you react to it. He is just checking your emotional balance. Few candidates burst at this declaration. Its always recommended that you maintain your calm. The interviewer wants to know how you react when adversity affects you or when you are unprepared to handle a failure.