Dont worry mate it was your first time, i did something similar in my baptism of fire at the ring (didnt go off on the grass mind).
I kept looking in my mirrors paranoid someone was going to hit me up the arse or that i was slowing everyone down, was focused too much behind and ot enough on the road.
Thankfully i was with bennett who was brilliant, he told me stop looking in the mirror, focus ahead, turn turn, break, break, go........
The other issue i had was i kept feathering the brake pedal as i do on normal roads. 2 laps in and i started getting deposits on the disks. Had to condition myself to be on then off the breaks.
Just needs more runs and experience, you will love it