Just finished a great book by Barbara Oakley on how to learn to learn. As I experience as a professor teaching courses that students consider to be difficult, many students do not know how to study effectively. Just reading books to learn mathematics will not bring you far. Dr. Oakley failed mathematics and science courses when she was in school, learned Russian and became a translator in the army. Now she is a full professor of engineering at Oakland University. What happened? She learned how to effectively learn the material she was interested in to learn.
An important lesson is to vary between focused and unfocused attention. Your brain keeps working on problems when you are not concentrated on it. It is important to start early with studying and make use of this background brain processing. Spending many hours in the last minute before an exam is very ineffective. And practice. Do your homework and practice. You don’t derive skills in sports or music by just trying it once, you have to practice!!
To get a brief overview of her book, see her Tedtalk.