Say no to distractions. Find time and space to do what you need to for your viva prep.
Say no to typos when you find them in your thesis. They don’t need to be your focus. Make a note and move on.
Say no to other tasks to free up rest time. Getting ready requires more than reading and reflecting. You need time to just rest.
Say no to your doubts, if you have them. Could you have got this far by being merely lucky? Could you have got this far while making serious mistakes?
The answer, of course, is “no”.