Leave things out, or just get faster?

Hi,

in my studies I have developed the habit to work through all the materials offered and therefore trying not to miss anything. With this I find myself often enough in exams realizing, that I may have invested too much time. At the beginning of new courses I always intend to restrict myself a bit and therefore just try to detect the "important stuff" and leave the rest out. So far not working. In respect of my future working career this gives me a bad feeling, as the workload surely will be much more and therefore one should be able to leave things out. On the other hand I have often read, that e.g. in IB it is necessary to avoid any kind of mistakes. May you guys share some of your insights or give me advice on wheter that should be changed or not. Or maybe I just have to get faster, so that I can work through everything in less time. Dunno, would be glad for your view..

Godspeed