Find three things that can help you feel ready on viva day.
Maybe your thesis, a notebook and a bottle of water.
Or a prompt card with keywords, your choice of clothes and a cup of coffee.
Perhaps your good day socks, a picture of your family and the most recent paper by your external.
Or your three things could be a mock viva, a lucky charm and a phone call to a friend.
More generally, find things to help you feel ready by considering work to help you prepare, things that help you feel confident and things that remind you of who are you (and what you can do).