Different To Expectations
Regulations, general experiences of PhD candidates and the more particular stories from people in your department create your viva expectations.
Every viva is unique, but yours won’t be a total unknown because it will follow – to some extent – the patterns of other vivas. Whatever you learn and whatever you come to believe, yours will not be a photocopy of the idea you have or a twin to a story someone else told you.
Find a balance for yourself in all this by getting ready.
A little knowledge (expectations) has to result in action (viva prep).
Having a mock viva isn’t a direct rehearsal for your actual viva: it’s not the dress rehearsal where everyone knows their lines – you’re getting a feel for the room, a feel for what it sounds like to be talking about your work and to be in discussion.
Your viva will necessarily be different to expectations – and in a way that you can’t expect!
All you can do is find out what you can, prepare as best you can and then keep going and being the determined, capable researcher that you are. That’s how you succeed.