What I usually try to do now is hype myself up before the interview, repeat positive affirmations and smile a lot. If I stutter, I tell the interviewer about my speech impediment and quickly move on. I had a really bad episode during an interview and I felt like shit for the two following weeks. The last interview was for a very important internship and it went great though, even if I stuttered here and there :). Believe in yourself, repeat positive affirmations before the interview, smile and answer the questions as best as you can. I believe in you.