Remember that you've started with a "pass", it's up to you to balls up the right stuff and turn it into a "fail".
The examiner is not trying to fail you.
If you do balls up on anything, tell the examiner. Fault recognition is vital. You can guarantee they saw the mistake before you did and by admitting it you are showing you're still in control. Don't be afraid to ask to re-do something.
Don't expect any special treatment from ATC just because you have an "exam" callsign. I was kept really high on my approach in order to get a couple of airlines in ahead of me. I did however tell the examiner what was going on and that I was high and what I planned to do, which was to get some flaps out and the gear down far earlier than "normal" in order I could descend at a higher rate and maintain speed control. I got good feedback on that during the de-brief, even if it didn't look pretty. It's what we do in a two crew environment so it's good practice anyway to mention out loud what you can see unfolding.
Remember to stay SAFE. If it's all unravelling you must ensure the safety of your passengers, you and the aircraft, know what the MSA is so you can at least climb to it if you find yourself in the sh1t. That is worst case scenario, I've never heard of anyone getting behind the drag curve to that extent but you'll need that "get out" for the rest of your flying life.
Oh and you'll never feel "ready". I've never felt "ready" for any of my tests including IR and Type Rating, but have managed to get them all first time. Even now I wonder how I managed to pass any of them based on what I have since learnt!
Personally I still think the IR test was the hardest thing I've had to do, far harder than my type rating.
Good luck