TBH I still to this day overdrive my car far too much, I generally find myself getting slower as the day progresses!
LOL
As I start to try to hard, it happens but not very often. TBH what I have learnt over my 2 years of racing is, Hitting the apex and hitting clean lines saves time. Overshooting 1 turn can cost 1-2 seconds more per turn!!
Smooth and flowing hitting your lines and not crashing will make you a better driver and you will get faster at doing it without noticing. Try not to focus on lap times for a few months, and focus on minimising your crashes and overshooting. And results will start to improve with minimal effort.
P.S. The worse thing to do when racing it tense up.. keep calm and don't overdrive and don't try to make up the time lost if you crash it will generally result in more time lost.