Survive means manage to keep going in difficult circumstances.
The viva is only difficult.
It’s a challenge, but not beyond you.
If it feels overwhelming, reflect a little on the challenges you’ve overcome during your PhD. How big were they? How challenging? How difficult? How many serious obstacles have you overcome to get to the viva?
The viva isn’t trivial, but it’s not impossible either. It’s only difficult.
And you can do difficult.