I’ve got a few questions for you: Did you do the work? Did you show up at the library or the lab or the office? Did you overcome obstacles through the tough times? Did you learn, did you grow, did you develop?
If you did all of these during your PhD, how could you be in a bad position for the viva?
It’s understandable if you are nervous, but it’s no accident that you’ve got this far. Keep going.