This may have been said already but it might be worth repeating.
If you've taken that step to come drive at a track event and you don't feel comfortable. get off the track.
Tell your instructor how you're feeling. Open up. Check your mirrors and maintain an elevated but safe pace back the pit and put your fist in the air. Get in and stopped and don't go back out until you're ready.
Meanwhile, analyze what it was that got you spooked. Too much traffic behind and you couldn't point them all by? Too much traffic ahead and you were getting squirrelly trying to keep your distance? Ask for clear track ahead or behind dependign upon your needs and rely on the track custodians to put you where you're at ease and able to work on your chosen area of improvement.
I've often found putting a faster car ahead of me has helped demonstrate differences that allowed that car to catch me. I've found other drivers in the paddock with similar cars and asked to try to grid together so we can learn from one another. Helping one another out is a common theme at different tracks and with different groups.