Congrats Nxsfan! I didn't sleep the night before my iva either, though I managed to nab 3 hours sleep in the morning. Adrenaline got me through it as well. And I didn't even sleep the night after. my mind was still racing so much!
My best tip is to read Tinkler & Jackson's book, to demystify the process. And reread your thesis, and note any errors. I took a list of them into the viva, and it was fine. And perhaps think about your answers to 5 key questions: originality of thesis, contribution to knowledge, methodology, weaknesses/gaps/mistakes, and what would I do differently if starting again. I found that much more helpful than thinking about dozens of potential (but often similar) viva questions.