Yeah, definitely try not to dwell on it too much. People post about getting accepted at somewhere they thought they bombed the interview for, as well as (actually, usually) getting rejected/waitlisted after amazing interviews. Preparing for your future interviews is the best thing you can do right now, especially in light of what did/didn't go as you wanted in your previous one.
I think it's really hard to tell what interviewers are going to see as the most important aspect about you, but you can help yourself by deciding ahead of time some important thing you'd like to convey (such as how you would contribute to the school environment, which is one of the primary things I'm supposed to look for while interviewing kids for my undergrad). In my most recent interview at one of my top choices, I was so nervous that I could feel myself shaking, and I was totally convinced that I had looked like a complete fool to the interviewer as a result until I got an acceptance letter =). Thank goodness poise was not on his list of necessary qualities in a future doc.
