Just try be as confident as you can, i was so very very nervous, but they do slip away slightly the further you get into it.
I had a very chatty examiner, who made me feel like i was just sat next to another instructor, although some people prefer that (being chatted to along the way) obviously not all examiners will be chatty, but it's not exactly a bad thing because you then can concentrate more on everything else. and Don't forget your mirrors when slowing down/speeding up etc etc
Try telling yourself it's just another driving lesson, i really convinced myself that it was just a lesson which made me feel slightly better
Not sure about anybody else but my test went really quickly, couldn't believe it when we were nearly back at the test center
Your examiner will have taught you well, stick to what you have learnt, you can do it, and will do it (: Good luck too