What would a perfect viva look like?
No hard questions? Being told you had passed at the start? Friendly examiners? A one hour time limit?
Just like the perfect thesis, the perfect viva doesn’t exist. You have no way of knowing in advance what your examiners think or what they have planned for the viva. Most people will have a positive viva, but it’s not totally within their control. However, you can control how prepared you are for your viva. It’s totally up to you, what you do to get ready, what you read or write or think. So don’t focus on what perfect might look like: focus on what you can actually do.