When we do things for the first time, most of us do not understand what we are doing immediately but later realise we should have done the other way to get desired results. Wish there was always second time in life, but unfortunately in the examination you have only one chance and you got to make best use of it by presenting your paper in an impressive manner.
Similarly, when you are going through the study materail you will find certain things very interesting and certain other things confusing. It is part of the mind game, which you need to take it in your stride.
Generally, a first time reading must be like a quick scan, where you are just trying to understand the enormity of the portions along with some concepts in your sub-conscious mind. The next time reading has to be a little more methodical, where you plan to devote time during the time when you can concentrate better. It is advisable to make your own short notes during this time and ensure you are able to revise it on a regular basis, so that you are able to re-collect what ever you have studied. These revisionary notes will helpful during examination day.
Considering the time factor, one may always blame we don't have so much time, but please understand that time is not a luxury and we need to burn the mid night oil, if necessary in order to reap rich dividends.
All the very best for your preparation.