When a candidate hears “defend your thesis” it’s easy for them to think of the viva as a battle, a struggle or a debate.
Perhaps a better way to describe the viva is that it’s a chance to support your choices. Your examiners have read your thesis. They’ve prepared for your viva. They have questions and opinions but the space is there for you to support what you’ve done.
You can clarify the unclear, add details or expand on your process. In sharing more of your research you have the opportunity to support your choices. So in your preparation be sure to check details that need checking, highlight details that are important and summarise anything that could make a difference.
The viva is one more opportunity to show what you did, what you know and what you can do.