Now imagine jumping into the middle of a real game filled with people who really know how to play. How will you do in that first game? Not so hot, huh?
Building a skill set in a way in which one can play effectively in a sport such as soccer, tennis, basketball, etc. requires many techniques. But one of the absolutely necessary ones is to scrimmage; practice playing in mock games to get a feel for the competition, put drill skills into practice, adapt technique, and learn to think amidst all the action.
So how come almost no students study for an exam by actually trying to do never-before-seen problems out of the context of which section they are in and in a timed environment? SCRIMMAGE FOR AN EXAM!?!? Well, why the heck not?
Examinations can be extremely stressful and frustrating. "I know this stuff! I've done problems just like these hundreds of times! But with only an hour to do 6-7-9 problems, I just blank! I must be a terrible test-taker."
I doubt it. Most of us can easily pass a walking test, I believe. But then again, we have been practicing that for a while now, right?
Try this next time: After each section is covered and HW problems done, grab a set of problems from that section which are of the same type as those in the HW assignment. Bank them (write them down without reference to the section they came from). As an exam approaches, take some out and under a specific time limit (10 minutes per problem in a calculus course, maybe?) do the problems without regard to notes, book, or any other source (be smart: do this in a place without ANY distractions).
If you can easily do the problems, then those types of problems are yours to jam on in the exam.
If you cannot, then you know what to study a bit more. In this case, study, wait some time, and then try again on a couple more.
Give it a shot. It's better than re-doing HW problems, or re-reading chapters five times over.
In bocca al lupo!