Realising that you’ve made a mistake doesn’t feel good. Spotting a typo, a mis-quote, an error or a problem in your thesis could send you into a panic. Or being told by your examiners that they have a question and finding that it is related to something you haven’t noticed could make you feel dreadful.
As with so many situations in the viva, all of the feelings could be much bigger than the situation they are in response to. If you’re wrong ask yourself why you are wrong. Ask yourself how you can make things right. Ask yourself what you need to do in the moment, in the viva.
Work past the feelings, engage with the situation and do something.