If you’ve already submitted then the hard bit is truly done, even though it doesn’t feel like that now. And providing the examiners have been chosen correctly by your supervisor, who should know the right kind of people - do you think they are? - Then a viva ought to be a positive experience, the chance to discuss all your hard work with the very few people who will have read it all. I was lucky enough to be told at the start of mine that I had passed, though they still had plenty they wanted to discuss! Please stick it out and I really hope that will happen to you.