How to get over failing driving test

Failed my first driving test a few days back for something I hardly ever do, I was at a roundabout and thought a car was going off at the exit before so I took that as an opportunity to go but the car didn’t get off at the exit and kept coming round resulting in the examiner having to dual control me which I knew at that moment was an instant fail. I keep going over it in my mind and it just brings me down every time cause if I had just waited a few more seconds to have definitely seen if that car was getting off at the previous exit I would’ve passed so now I have to wait until January to resit which also means I’ll have to sit the new test. Does anyone have any tips or advice or similar stories? Thanks!