I am writing my maths personal statement, and I've written a lot about things I've done, but I'm struggling how to express why I actually find these things interesting. I genuinely do find them interesting, but I can't place it into words why I do. I just sort of do.
I've just sort of said: "I did x, found it interesting, so then I did y" throughout
Aim to show, rather than tell. Demonstrate your interest by talking about what you did, and then why you did it, how that led you to other things you did and/or changed or enhanced your understanding of the subject. So rather than simply just describing what you did and saying it was interesting, giving the rationale behind choosing to do it (why that topic/book/project/etc? Why not something else?) and your reflection on the outcomes/aftermath of that illustrates your interest itself