You might have to take a step back when writing up to really ask yourself, “What else does this need?”
You might have to take a step back from your thesis at submission, to give yourself space to reflect before your viva.
You might have to take a step back from your PhD at submission, so you can rest and restore yourself.
And you might have to take a step back from yourself and your research in the viva. A question could seem unfair, it could seem too critical, but remember that any question in the viva is being asked for a good reason.
A step back helps to nudge your perspective. You might need to take several steps back as you finish your PhD, but they will all eventually help you move forward.