Even if you think you know it all, read your thesis before your viva.
Even if you’re sure there’s no way you’ll forget any of your corrections, take a notebook to the viva.
Even if you’re sure your examiners won’t ask about this or that, be sure you take a look at this and that before your viva.
Even if you don’t want to rehearse with your supervisor, find some useful way to practise responding to questions before the viva.
Even if you’re nervous, go to your viva and succeed.