There are lots of necessary breaks before, during and after your viva.
When you submit it’s good to pause from looking at your thesis and thinking about your PhD research. You might have other research work to do but at least break from looking at your thesis. Then you can have a fresh perspective when you come to prepare for your viva.
During the viva there are lots of good reasons to have breaks, big and small. A micro-break could be to simply pause while you consider a question or look for something in your thesis. A regular break in the viva could be to use the bathroom, compose yourself or attend to any medical need. You can always ask your examiners for a break.
And after your viva it’s likely your examiners will ask for a short break so they can discuss what has happened and what they need to do now to complete the examination process. While they talk about your corrections it’s a good idea for you to plan ahead to do something – get some water, use the bathroom, get some fresh air – so that you’re not simply waiting.
After your viva is done, try to take a break if you can. A little time out can help you appreciate the milestone you’ve reached and refresh you for the next stage of your journey.