Yeah, job interviews are tricky and I've blown a bunch. This last one I threw caution to the wind and, again, tried a different approach. When they were close to "done" asking me the standard questions, I stopped them a minute. It sort of went like this...
"I know that interviews like this are intended to find out who I am, and that's important. But it's also to make sure you don't get someone you don't want. So... let me tell you who I'm not... I'm not the girl that watches the clock and hits the door running just because my time is up... I'm not the girl that brings her social life to the office... I'm not the girl who needs to be babysat and told each and every task to do... I'm not the girl that.... blah, blah, blah"
I was told in spades later that they had already decided to hire the girl before me and I got the interview only as a courtesy.. and that THAT ^ was what got me the job. It totally blew them out of the water. Adjust as you see fit. And at the end of it I ended with some kind of joke to make them laugh.. probably something like "I'm not the girl that can walk away from chocolate cake, so if you have a lot of that here, it could be a deal breaker for me".
Feel free to borrow, and good luck! Oh, and I'm fat, and was 49, AND had NO medical experience and they hired me anyways.