This is perhaps the simples secret and also the most obvious.
That is why perhaps it is missed by almost everyone.
Almost every student [and others, too] tries to learn more and more things from more and more books and since time is limited, they learn less and less from each.
What is much more easier, faster, and effective is to learn more from less, which means from less books, from less gurus, from less teachers, as well as less topics and less subjects.
Try it for one week. Limit the number of books and the numer of things you try to learn. And, try to learn more of less, so you can spend more time and become better at it.