Stress can be a response to things out of your control whereas nerves can mean you care about your result.
I hate to be the party pooper but every athlete is going to have challenges before and/or on race day - whether it's the weather, terrain or something outside your control or feeling really, really uncomfortable because you are giving a hard effort.
Don't assume you are going to have a bad day because it's windy, hot/cold or rainy. Race day rewards a great effort and a smart execution.
Don't waste away months of training on worries, doubt or fear.With the conditions you are given on race day, be sure to race your nearest competition with your current level of fitness.
The only time you will know what you are capable of achieving on race day is when you cross the finish line, knowing that you gave your absolute best effort and overcame everything that you experienced on race day.
When you race, your entire race is built on steps, with each mile affecting the next mile. While there are many things within your control, holding x-watts or x-pace to give you x-final result is not true racing.
Don't stress about the outcome.
The best race day outcome is determined by how you manage what you can control and how you overcome what you can't control.... from start to finish.
Enjoy the challenges that you will experience on race day and don't stress out before you start your amazing day with your awesome body.