Another chance to show up, do good work, show and share your knowledge, your ability, your insight.
By the viva you will have had hundreds and hundreds of days where you have done this. So while it’s an important day, and it’s essential that you do show up with your knowledge, your ability and your insight, it’s overwhelmingly likely that that’s exactly what you will do.
Because it’s an important day, you might show up with some nervousness or worries too. That’s fine. You can handle them for your viva day, for one more day. Draw confidence from the fact that you couldn’t have got this far without doing something well (whatever that particular something might be for you, your research and your thesis).
One more day. You can do it.