Stress
One would think the stress would end after the golden call ! Anyway as long as your sure about your good health the rest is just in your head lol (who am I kidding).
As for your interview Dress well , business with Tie and short hair no gel, smile as much as you can, listen and respect others when they give an opinion, and if you really want the job it will show and you will be OK.
Keep us Posted.