So much worry is put on the viva, that many candidates overlook the idea that it could be really, really good.
You could get new ideas for future research. You could get validation from high-standing members of your community. You could get feedback and opinions that will help. You could get ideas of how to be a better researcher.
You could even enjoy it.
If you spend a little time worrying about your viva, at least try to balance that and spend some time thinking about how good it could be.