I always thought the 'just be yourself' was common sense and easy to do. But as I look back, my worst interviews were the ones where I got too caught up in the mechanics and didn't just go in and relax and just be myself. By mechanics, I mean over-preparing and stressing about researching the school, looking over potential and past questions, remembering what questions I wanted to ask them, etc. I was too worried about not messing up than just being myself. I just never let go of that and it made the conversations weird and I was probably more nervous than I should have been.
I'll probably mentions this throughout the cycle. It doesn't matter at all now, but my mind still dwells on it.