Think of it this way: they might be asking most of the questions, but it's not just a one-way interview. Take it as an opportunity to interview THEM - do you really want to go to their school? Do they have what you're looking for? That awful, aggressive question the interviewer just asked you - geez, doesn't she know that she's giving you a bad impression of the school? Sure, it might seem cocky, but it'll make you feel more in control of the situation.
Most importantly, go into interviews ready to tell them very honestly and forthrightly who you are. No excuses, no apologies. Don't focus on the few things that lacking in your application; think of everything you HAVE done - all those hours you've slaved away to get to where you are now. Be genuinely proud of all your achievements. It's all about getting into the right mindset!