I had first hand experience with this at that same race. I showed up late in the practice session to a track I had never been on before, got set up, was able to run 3 minutes on 4 of the 6 six lanes and then qualify. Luckily, qualifying was on one of the 4 lanes I ran on. I qualified second to last. The first race I finished 15th out of 18. I had the same result in the second race. However, as my time on the track increased, my finishing position started to rise. The third race I finished 13th out of 17 and the fourth race I was 11th out of 17. All of this happened while I had almost no time to adjust my car to suit the track. It turned out that, while my car wasn't the fastest, it was competitive and my knowledge of the track grew. Experience is king.
As I drove home that night, I was able to feel good that I learned quite a bit that day and would be able to bring that knowledge back with me the next time I raced there. In addition, any track time is useful track time, especially in a competition environment. Take a deep breath, get in your rhythm, race the track, keep lady luck on your side. Experience is king.
Here's a video of the most recent race I attended, courtesy of Jeff Hurley.