Everyone is nervous on their driving test - and I mean, everyone! Shaking legs (to the point of not being able to control the clutch), dry mouth, sweaty palms, dry mouth, beating heart, feeling sick and faint (sometimes even being sick). So it may one of those occasions where everyone is on a level playing field!
So, you can't beat the nerves, so don't even try. Accept that you and your nerves will be doing the test together 
. The sooner you accept that, the quicker you can move on with the important stuff like driving well.
The examiner will want you to pass as it is less paperwork for them, so they are on your side straight away! They are not monsters who eat kittens for breakfast - and you can have a natter if your concentration allows.
If you think you've done something wrong, carry on as if you haven't - you have no idea how it has been judged, and worrying about it will only affect your concentration for the rest of the drive.
If you don't get it this time, you only have to wait ten days to do it again so it's not the end of the world.
Try to enjoy the experience. Good luck 