Oh yes the fun of a road test. I hated those, I always got the one who had a reputation of failing people for any reason she could find. That didn't help at all, she actually failed me twice. The first time was when I took my road test right after my brother, which everyone said was a bad idea. The second time she failed me is because I refused to do a 3 point turn on a narrow through street that had cars parked on both sides. I did get one instructor that was very nice, she put me at ease.
Taking someone with you is a good idea, if they allow it. Sometimes being honest with the instructor and just tell them you tend to get nervous and anxious. They know people tend to be like that anyway and they may help to put you at ease. Some may not just care so you'll have to keep yourself calm. Just pretend you are with a friend who's giving you directions. Don't picture them in their underwear though, most of the time that ends up adding to your anxiety.
With jobs, oh man the interviewing process can be nerve racking. I hate that process too, and having conducted interviews I can tell you it isn't always as easy either. Grant you, you have control over the interview but you never know who's walking through that door more than what you've read on paper. I've had that experience a few times, they look good on paper, then come in and I think...why am I wasting my time on this person. Again, it isn't always a bad idea to admit to being nervous (just don't go overboard), the person you are talking to has been through the same process at one time. Having been on both sides of the process I like honesty from people.
The big thing is building up your confidence, a lot of people get nervous, you won't be the first and everyone makes a mistake. When you do you can't let it discourage you or you make more. You just acknowledge it, correct it if you can, learn from it, put it out of your mind, and move on. And trying not to let the person on the other side intimidate you, sometimes that is their job.