Keep eye contact, and be perfectly honest.

I am going through the same thing. My confidence is there I keep eye contact and conversation going, questions are all answered. As much as I think and believe it went great at least better than when I got hired before. Before I used to be nervous and did not always answer the way they wanted and I was okay getting jobs. Now I have more experience, more experience and I even send a thank you for your time email. And I am still looking. Sorry this did not help much but if anything I give you is, do not stop trying, keep looking keep going and you will find one that is right for you. and do not be afraid to also say no if it does not fit your needs as well. Good Luck