I find that the following scenario happens to me quite a lot in my studies as an advanced undergrad: I take a relatively difficult course and do well in it. Eight months down the road a specific topic from the aforementioned course is brought up in my current course and I have completely forgotten said topic. I then find myself backtracking and taking close to an hour or two relearning the topic. Is this "normal" for those serious about mathematics? It happens to me more often than not and I am too afraid to ask my direct peers for fear of them finding out just how much I lack in memory management.
So does this happen to you all? And if so, how do you best make use of your "retraining" period?