Hi! I passed my test first time a week ago with 2 minors. I was pretty much like you - even the lesson before my test (which I would recommend doing) I was messing up on manoeuvres.
1. RELAX. It's easier said than done I know, but try not to imagine things going wrong, but instead going right. About 10 minutes into the test you will feel yourself relax and it'll start to just feel like another lesson.
2. Obvious, but really focus on your mirrors. Check your rear-view mirror every few seconds and make sure to check your wing mirrors when moving out, before indicating and when coming off of roundabouts. Every-time you are asked to stop on the side of the road, check mirrors before indicating to stop. During manoeuvres, make sure to do all round observations (mirrors, blind spots) every time you stop.
3. Know what happens during the test. The examiner should explain what happens during the test, but knowing beforehand is good. For example, you should know that you are asked to do 1 manoeuvre, do 10 minutes of independent driving and that they may make your do an emergency stop etc.
4. If you think you failed, do NOT let that affect the rest of the test. I thought I failed pretty much straight away (he asked me to turn left, I couldn't see it till the last second and swerved into it really quickly), but I didn't even get a minor for that. There were loads of points as well where I thought I'd failed or got a minor but didn't.
5. You can get minors! You do not have to be perfect. Just safe. Remember, it is better to hesitate and get a minor, than pull out when you can't and fail. One of my minors was for doing another reverse during the turn in the road but I wasn't sure I could turn enough without hitting the curb in front (which is usually instant failure).
6. Take your time, especially with the manoeuvres. There is no time limit on how long you can take to do them.
7. Remember you can do it! If your instructors think you are ready, then you are ready! The only thing stopping you is your worries.
Sorry for the essay :P
Best of luck, keep us updated how it goes!!