Remember that thesis defence doesn’t mean that you need to protect your work from harm.
Remember you’re not in a courtroom with your thesis on the witness stand.
Defending your thesis means you are tasked with speaking up for a silent book.
The words are all there, but maybe they’re not all clear. The pages are packed but there could be more to say. You have every chapter you need, but your examiners might want to know a little more or talk a little more about the fascinating things you’ve laid out.
In the viva, your task is to continue to support the work you’ve done for a long time. Defending your thesis means supporting the ideas you’ve developed and saying more about why they’re valuable.