At submission you can apply everything you’ve done and learned to make your thesis the best it can be. It takes time but you can do it because you’ve been doing it for so long already.
After submission you can continue to do the work of a researcher in your field. You can take a little time to get ready for the viva.
During the viva you can take what you’ve been building for years and engage with your examiners. You can continue to prove yourself, despite doubts and worries.
There’s a lot to do but not too much. Not for you. When you face a challenge or problem, remember that you could only be facing a situation like this because you have already done so much – and you can do it again.