I had my driving test (first time) today. In the days leading up to the test I was pretty confident I'd fail as I didn't feel ready, and during the test I KNEW I had failed with the number of mistakes I made. I actually passed and with only two minors! Couldn't believe it. My gear changes were slightly shuffly and fudged, I was unsure about the speed limit of a couple of roads, went in the wrong gear once (although changed back in the nick of time), got beeped at on a roundabout when turning off, nearly mucked up the hill start - the list goes on. I asked her about these mistakes at the end and she said I was being far too critical of myself.
First of all - it's not nearly as nerve-wracking as you imagine. The examiner should be friendly and nice to you throughout, and they shouldn't react to any mistakes you think you made. Mine just sat there peacefully and at no point did I feel like she was judging me for being crap. It's all just in your head.
With regards to junctions - this was something I was worried about as my instructor's always nagging me about hesitation at roundabouts/junctions. If you're in any doubt, wait. If there was a big gap where you think you should have gone, it might be worth saying to the examiner something like "I know there was a gap there, but I figured that it would be safer to wait, especially as we're turning right on to a main road" - if you explain your decision, they're more likely to be lenient as they know you have an understanding of what you may have done wrong. I did get a minor for pulling slowly out at a crossroads, but that was it.
The test went so much quicker than I expected - even though I thought it was going awfully, it ended quick enough that I didn't have too much worrying to do. The most important thing to remember is that they aren't looking for you to drive perfectly (I certainly didn't), they just want you to be safe. The odd mistake (hitting a speed bump badly, bad gear change, braking too harshly) here or there shouldn't make any difference overall. It's just so subjective- what may be appropriate in one situation may not be in another.
Good luck, I hope you pass