If it is any consolation CG I think we all felt as you do in the early days.
I can still remember the heart rate at what seemed to be 500 beats per min as the flag was about to drop, the sweaty palms and the cramp in my forearms after only 10 laps!!! By the end of a 25 lap race I was a physical ( and mental) wreck. I had to go and take a rest afterwards............all over a computer game!! lol my wife thought I was going crazy!
The one thing I started doing that helped was to get into a regular pattern before the start of a race.
It went something like this............
Always do the last few laps ( max 3) on race fuel , that way you are dialled into the car on cold tyres and full tanks for the start of the race.
Don't keep lapping until GPL kicks you off to start the race, better to retire to the pits with maybe a minute or two still left in qually and relax. Maybe take a good drink of water or squash as your brain and body are going to need it!!
In that 2 minutes check that you have got your race setup loaded and the
correct fuel loadedWhen you join the grid don't sit there revving the engine like a boy racer, sit calmly and quietly and watch the timer count down to 10 secs. Force yourself to relax with a few deep breaths.
With 10 secs to go take your hands off the wheel and shake and relax them, then gently place them back on the wheel being concious not to grip it to tightly.
Then turn your concentration on the starter.
Only build your revs up as the starter raises his flag and concentrate on the flag, ready to go as soon as it drops.
For the first lap just concentrate on being smooth and safe as the tyres warm up, watch the cars ahead for spins and contacts so that you can avoid them.
I used to pick a fellow driver who was maybe about my pace or very slightly faster and during the race my aim was simply to be able to see that other car at some point during each lap. That way I learned to be consistent with my lap times and gradually I picked up pace. ( I never told those drivers who they were, but as I improved I moved my sights higher up the grid
)
I have always maintained that your biggest adversary is the track itself. Concentrate on not letting the track beat you by driving within your speed/ability. Remember each error that takes you off track loses at least 20 secs, so better to be 0.5 secs earlier on the brakes , and get cleanly around the corner
Don't misunderstand me, I do not find GPL boring after all this time, far from it, but I have learned to do the Zen thing and relax muscles and mind and "feel the force"!!! Yes there is still a tingle at the start of a race and I am sure that my heart rate rises, especially if I get into a really close duel with another driver (s) that is finely balanced. That I guess is the beauty of GPL, it still excites after all thsi time!!