Your Best Is Enough
If you can honestly say that you tried hard, learned lots and did the work for your PhD then that’s enough. If you can say that despite challenges and obstacles, setbacks and worse, that you did your best throughout your PhD then that’s enough.
Your determination, knowledge and capability helped you to keep going. That will help you to get ready for your viva.
Ultimately, it’s what will lead you to succeed in your viva.
Your best is enough.