When you’re getting ready for your viva ask people who know about vivas. Get specific help rather than general impressions.
When you’re getting ready ask people who know you for help. Ask friends about their experiences and for a little of their time. Ask your supervisors to give you their considered thoughts about your work and about the viva itself.
When getting ready ask your institution for support. Ask them for the regulations, check what things mean and learn who to talk to in case anything goes wrong.
Above all, ask the right questions of the right people. Look around widely for support, but ask people you can trust first: you can trust them either because they know you or they know what you need to know.