Most Vivas
Most vivas are not too long. They regularly result in minor corrections. They most often have two examiners, with a possibility for an independent chair as well. The great majority of vivas result in success.
Remember all this, but also remember that your viva will be unique. Your research, your contribution and you are all unique elements to your viva experience.
As you prepare, take time to reflect on what your viva will likely have in common with every other viva. Be sure to focus on what makes your contribution and journey unique too.