I enter each interview the same way thinking they already are interested, all I have to do is convince them. Your qualifications have already sold your ability, now they want to meet the person. I've been interviewed and done interviews, and at the interview stage it's 9 times out of 10 more about fitting in with the team over qualifications. If you weren't qualified, you wouldn't be in the interview. So be yourself. If you are not hired, it's not bad. You probably would not have been happy in the position if your personality didn't fit with the rest of the group anyway! Good luck!