In your records you see your story, even in outline.
Got a lab book? Read it. Kept a diary? Give it the once-over. You probably have an electronic record of meetings with your supervisor, right? Look over those notes.
What do you see? Ideas? Plans? Objectives? Successes? Failures? Goals unmet? Wins, big and small?
The broad strokes of a talented researcher doing something good. Look at how far you’ve come.
It’s your story. Use it to be your best self in the viva.