Get some water/a favorite drink when you're in the airport to carry on the plane with you. If you like licorice or candy, bring it with you. These are my rituals and comfort me when I'm getting ready to get on the plane. I'm focused on something other than the flight itself.
"I need to get XYZ before I board..." I also have something to DO (drink or munch) while on the plane, versus sit there and work myself up.
Remember to breathe. Focus on breathing in and out while on the plane. There's nothing you can do in your seat to fly the plane, so let the person who has driven the plane thousands of times do their job. Relax your body one spot at a time, and just realize there's nothing you
need to do but sit in the seat and be patient.
Don't think you need to worry. Pay attention to the trained professionals, follow their instructions, and just be patient.
I've flown a ton of times, but I struggle with being nervous.

I hope all that helps!