No way your thesis is perfect.
No expectation it should be either.
No chance you’re not an expert in your research.
No way to predict exactly what will happen in the viva.
No excuse for not having expectations either (there are lots of people who have had them before!).
No examiner has lived through doing your research.
No possibility you got to submission without doing something good.
No way you can do the work without being talented.
No chance you’re not ready when the viva comes around.