I'm not at the stage of a flying skills test yet, but from previous skills tests in other forms of transport(cars, boats, trucks and motorcycles) the important thing to remember is that you've done it dozens of times before and you know how to do it. Think what you have to do and not what not to do and remember the guy next to you is not trying to fail you but simply there to check if you're safe enough to operate the machine.
If it makes you feel any better, I ignored my own advice and the outcome was less than positive. I have two stories, first one was when I did my motorcycle test and second is more recent and related to flying. This was almost 15 years ago, I was going for my first of... well I rather not say how many attempts I had but it was quite a few, attempts at my motorcycle license. I had about 40 hours of riding by then both with instructors and my dad. I was doing everything pretty much perfectly. Brilliant slow smooth figure 8s, strong confident emergency braking and good road sense. I decided to go for my test at that point. I failed miserably. I locked my brakes on the emergency braking test, I dropped my bike doing a figure 8 and I nearly ran a stop sign. I eventually worked out this was due to my preoccupation of what might go wrong rather than thinking what I should do. I fixed my mind set and I had no issue with my other skills tests. Fast forwarding 15 years, I'm now doing my PPL. At some point, I had done 5 very good landings without really any input from the instructor. After the last good landing he turn to me and said, "That last one was all you, do that again I might have you soloing this afternoon" The very next landing ended up a bit of a pancake. I was so preoccupied with what I shouldn't do that I completely shutoff all common sense and did all sorts of weird things like forgetting to put down flap and rounding out too early. I completely forgot my own advice and the result was a very ugly landing.
Anyway hope the weather is favorable for your test and you don't need luck because you know with your skills you make your own luck.