Don't bring the "pain" to the painful interview
When interviewers believe that a 20-minute interview lasted for two hours, despite how the clock reads, the interview has gone wrong -- really wrong.
Is it possible to devise a contemporaneous repair for an interview meltdown? Probably not, although once you have diagnosed the disaster, you may meet the interviewers later in life and laugh at yourself.
Can you be prepared for the next interview? Yes, if you can answer one question and be prepared to discuss one subject:
ONE QUESTION Why do you want this job? Not "Why do you want a job?" but "Why do you want THIS job?" Interviewers need to know that you have thought about the place in which you will work and the work that you will do.
ONE SUBJECT with three parts What three things do I want them to know about me before I leave the room?* When you have to struggle to name two, and then you sit, clicking your tongue, while trying to puzzle out the third, the interview has gone irretrievably badly.
*For an extended discussion of the three things you need to communicate to interviewers, consult Kimm Walton's Guerilla Tactics for Getting the Legal Job of Your Dreams.