Hold On
If you feel confident in the days leading up to your viva then do what you can to hold on to that feeling. Remind yourself of what you’ve done to come so far. Remind yourself of the difference your work makes.
If you feel certain of what to expect from your viva then hold on to that certainty. Make notes for yourself of what others have told you. Write down what seems most relevant from the regulations.
If you feel ready to talk in your viva then hold on as much as possible. Rehearse for your viva. Read your thesis and write summaries. Keep going with your preparations to keep that feeling alive for yourself.
Hold on. There’s not long to go and not much to do before you finish your PhD.