Was it reading everything you did to understand your discipline?
Was it finding ways to frame questions for your research?
Was it difficult getting to grips with methods and processes?
Was it tough to write your thesis?
Anything that’s hard at PhD level is valuable. It has to be. It’s either valuable because it’s practically hard, taking time to acquire skills or understanding, or it’s valuable because it’s original. Anything you’ve found hard during your PhD (even if you find it less difficult now) is valuable.
Valuable is a sign post leading in the direction of what makes your research significant: why it matters and what kind of a difference it makes. Take time before the viva to think about what was hard. You’ll unpick some of what you’ll need to talk about with your examiners.