Unlike most other subjects, math is cumulative: students are taught one technique, they practice it for a while, and then they're taught a second technique that builds on the previous. So there are two skills required:

*The discipline to study and practice a technique until you understand it and can apply it easily. *The ability to close the inferential gap between one technique and the next.

The second is the source of trouble. I can (and have) sat in on a single day's instruction of a language class and learned something about that language. But if a student misses just one jump in math class, the rest of the year will be incomprehensible. No wonder people become convinced they're "terrible at math" after an experience like that!