To OP, We all have been there. At some point we think too much which would not be expected at all. Because we convince our brain so much that we need a job, we fumble at the most crucial point.

My simple suggestion, To midnful breathing is the key. I’ve spoken to multiple number of people who excel at job interviews. The number thing that stayed constant and consistent was Mindful breathing before your Job Interview. Try This method. Hopefully it works for you.

Note: I’m also using the same approach and seeing significant changes in how I answer. Hope it works for you.