Rent a funny movie, take a bubble bath, read a book, spend some time with friends...or something else you find relaxing...
You will be surprised at the number of people in your classes who are in the same boat.
Lecture and classroom time really aren't any different from any other type of class. You listen, you work in small groups, you take notes.
Clinicals are the hands-on part of this, where you can gain skills, learn to manage your time, and begin to feel comfortable with the process. You'll start off slowly and get more responsibilities as are ready for them. You won't be given so much to do all at once that you have a meltdown...and you may even be working with a partner when you first start out.
Listen to your instructor, ask questions, respect the patients and the nurses. You'll do fine.
The worst thing that happened to me in my first clinical rotation was that I got stuck on the elevator for a couple of hours with someone who was claustrophobic...although I got to do a nice intervention, this activity was NOT planned by our instructor!
A woman who graduated with me, and who is now a fantastic nurse, was a waitress when she started nursing school
-- what she learned in waitressing ("Full hands in, full hands out") translates very well to nursing...once I really got this down, it saved me a lot of steps. Unfortunately, she didn't share this until my 2nd year!