Our teachers taught us right

to write notes. to take down notes. to keep notes.

why is that the case?
apparently (and i agree to this point of view) in the process of noting down things (that your teacher is trying to teach), even if you fail to comprehend it at that moment in time, the knowledge's imprint will be left on your consciousness.

and someday, some time, in the future, be it 3 years' time, or 300 years' time, some event or smtg will trigger that imprint, and you will have the realisations that your teacher is trying to teach!