How did you manage to learn anything at uni?

I'm self learning maths through books and what not, but I couldn't possibly imagine how someone can learn this stuff at university.

Im taking my time, going through various undergrad textbooks. But what I'm surprised about is how whole, massive textbooks are blitzed through in one semester, can't imagine learning anything at that pace.

If I had chosen maths as my course, I probably would have failed.