You’ll probably be doing this in the viva. Saying similar things to what you’ve said or thought before. Rehashing old arguments and reasons. That’s OK – the viva is about exploring what you did and what you can do, so there’s bound to be an element of covering old ground (for you).
You need to do this in preparation of the viva too. Reading your thesis again, checking old notes and making new ones that summarise points. Checking papers you’ve read. Rehearsing with friends or supervisors the kinds of things that you might say in the viva itself. That’s to be expected.
But you could be repeating all through your final year too. Carefully, calmly repeating to yourself: I’m doing this. I’m good enough. I succeeded when I did X. I did something important when I finished Y. This chapter is good. I’m good. I’m good enough.
Repeating to yourself that you’re good enough isn’t magic or wish-making: it’s repeating the truth. It’s a reflection of yourself. Repeat the truth of how you’ve got this far, and you’ll find the confidence you need for your viva.
(this is a message I share a lot in my work, but let me know if you need to hear it again)