Hi,
IMHO, butterflies should go away for your lower priority races once you've gotten a hundred or so races under your belt. I still get kind of anxious when I'm in a race where I either think I can do something or when there are a lot of big guns (vs. the usual some big guns) in the race. Also I am initially nervous when I'm racing on a course for the first time. However, after a few laps that goes away.