In maths, hard work alone won't get you far without that understanding of what the hell's going on. I was the sort that learnt the 'formula' for solving problem type X by doing it fifty times. It works, 80% of the time.
But for that other 20%, you've got to spend the time to really get it and figure out why you're doing what you're doing. This requires thinking deeply, watching vids that explain it in different ways, creating analogies and models for it, and really trying to visualise what's happening in 3D.
For most of us, it takes heaps of time and effort to really THINK about what's going on and why. For the geniuses, a short explanation and a few moments of thought is all it takes to 'click'.