100% agree this is something you grind at. Calculus, even multivariate, and even the stuff beyond that, still grind. I used to be really good at it, definitely not the best but among the higher scores in my college math classes. But 10+ years later, when I go and look at stuff that would have barely fazed me then, I go cross eyed now. I remember the concepts, vaguely, but following the math and linking together the various theorems and transformations feels like wading through syrup. It’s a problem for me as I’m trying to dig into data science stuff, and it feels like getting back into marathon shape after 10 years of not running.

There’s absolutely a component of learning the concepts, but a huge part of being good at the math is just building up the mental muscle memory for symbolic manipulation. Sure there’s innately talented people out there, but the consistent application of incremental effort will get you very far regardless of talent.