Keep a tiny journal for your prep. Every time you do something, add it to a growing list of what you’ve done in pursuit of being ready.
Lots of viva prep tasks don’t have a visible output: when you have read your thesis or a paper you only have a memory. When you talk with a friend there’s nothing physical to point so you can say, “I did it.”
So keep a little journal. It doesn’t have to be more complicated than recording what you did, when you did it, why you did it and how it helped.
Build the proof for yourself that you are getting ready for your viva.