I'm probably not the best person to respond cos I get really neurotic about interviews too, but I try and think of all the positive things you can bring to the job, what have you got to offer that will put you above everyone else? Try thinking up some good questions to ask too, that always goes down well.
A good distractor always helps too, stick your nose in a good book for a couple of days if you can, or do something that you enjoy that will take your mind off it. I tend to take Kalms for a couple of days before, they help me sleep better
Hope that helps a bit, and good luck