This is so true especially if you force your mind to absorb all the things that you need to review for your tomorrow’s exam. Why? Because a person typically forgets as much as 80% of what he or she learned within 24 hours and according to a research, memory retention is enhanced by sleep. And now it is clear why all experts are encouraging students to relax and sleep early the night before their exam instead of having one final round of night-review.
Aside from depriving yourself in getting adequate sleep when you study just a day or a night prior to your exam, you are also wasting your time as there is no guarantee that you can retain what you squeezed into your mind. You are doing no good for your body and your mind when you force your mind to absorb the whole book or your entire one month lecture in just one sitting.
So stick to the good-old formula of studying: establish a regular study habit whether or not you have homework or exam the following day. Studying this way is not only easier and shorter (2-3 hours daily) but also let you master and retain all the necessary information on a particular subject.