To reduce nerves in a league race, I would suggest practicing the first lap from the grid with race fuel and setup. If you know your grid position, even better. If you have all your braking points and lines around the corners committed to memory, the first lap should be easier. If possible, try practicing on a public server too, to get used to driving in traffic on the track. The first lap will usually be 'exciting', but thereafter just settle into a rhythm. A consistent driver is often just as effective as a fast driver who loses time when having an off.