After your PhD, tell others what you learned. Not just the ideas in your thesis, but what you’ve learned about working well. What you can do now that you couldn’t before. What you learned at the viva even: what that experience was like for you and what you think it means.
Write it down so you don’t forget. Make a page in a journal to summarise how far you’ve come. Write a blog post. Give a talk before you leave your department. Do something to mark this change: you’re now a PhD!
Your story could help others write their own.