My 2-cents worth
I have a couple of general ideas/thoughts that helped when my kids were first starting. I told them to worry less about how they did against everyone else, and to concentrate on improving their times. We timed them on each track, and even sections of the track and broke those sections down to manageable groups, then worked on those areas. You can't always do that, unless the track isn't nuts busy, but we have a track here we can, and it helped. They were able to run a section 50 times in an afternoon, instead of running it 20 times all day, if they ran the entire track. Like I said, you can't do that everywhere, but we could here. What we noticed, even on tracks where we had to run the entire track to be safe, when they ran against themselves, using only the clock as a guide, and working different techniques and lines in those areas, they progressed, and gained confidence as their times improved. As for the nervousness, well if that ever went away you probably wouldn't do it anymore. Hope it helps. Good luck.