The viva: hundreds and hundreds of days of work that come down to one day. One day when you have to do well.
That could sound very worrying, but remember that all that work is the price of admission for the viva. You have to invest all of that time and effort to get that far. It’s not idly or blindly spent; all of that effort helps to make you ready for that one day with your examiners.
One way to look at the viva is telling yourself, “After all this time, it all comes down to this!”
A more helpful story is to think, “After all this time, I’m ready for this!”