The post covers a great mindset, but the math really is one thing, and learning how you learn and how you can learn is invaluable.
This is a great course to start learning about your learning.
https://www.coursera.org/learn/learning-how-to-learn
After/with this, there is a slew of adult learning knowledge that will likely make you feel better.
One key is learning to understand something, before learning to memorize it.
Another is creating your own mind map of how the concepts you are learning fits together.
Farnham street has some great books on mental models as well that was recommended to me as helping
An expert is someone who can often explain complex things in very simple ways. being an innocent beginner is one of the best mindsets to cultivate - you learn what you do and don't know pretty quick, and also a sense of known vs unknown, and size and number of unknowns.