If it won’t cause pain or upset, think back to who you were when you started your PhD journey.
Consider what you knew and what you could do, and compare that with your capability today.
Being ready for the viva is partly all the work you’ve done, partly the specific preparations for the viva and partly how you feel about yourself and what you can do. A PhD journey can be long and difficult; sometimes, when reflecting it can be natural to remember the beginnings or the harder moments.
Instead, remember where you are today. Remember the skills, the knowledge, the talent and the success that you have. You are not the person you were. You are not who you were when you began.
Now you can do so much more.
You know so much more.
And you have achieved so much more than when you started.