best of luck, not that you will need, your instructor will not put you in for it unless he thinks you can pass.
Take this attitude, when you have stepped in the aircraft you have already passed, it is up to you to fail, not the other way round!! Doing this makes it seem less of a mountain to climb.
The best advice I can give though is this, if you lash something up don't, I say again (good RT) DON'T, hope the examiner didnt see it and keep quiet, tell him what you have got wrong and why it happened. He is not there to fail you or trip you up in any way, he is there to make sure you can fly in a safe manner, can handle a few basic tasks and fly the plane. Safety is the key, my examiner told me all he does is ask himself the question at the end of the flight "would I let my kids fly with the person" if the answer is yes then you have passed.
Also remember it is not like a driving test, what you are being examined on is are you in a good position to have a "licence to learn", they are not looking for airline level flying, just safety.
I lashed up a couple of things really badly (diversion and steep turn) I realsised my diversion was wrong from a ground features check, told him I had got it wrong and what I was going to do about it, and we got to the overhead of the diversion field without any further problems. When I descended nearly 500 feet in a steep turn I told him I knew I had lashed it up and asked if I could do it again, all went well the second time and away we go!!!!! On the ground I had passed first time out, because although I buggered parts of it up, I knew I had and put it right, and therefore operated in a safe manner!!
Above anything else, just enjoy the ride, and we look forwards to you teling us you passed tomorrow!!!!