I am an undergraduate student in Mathematics. I am writing here because I think I have a problem in the way I study Math. My grades are pretty good, but I think that I am not able to effectively remember what I studied.
I will try to explain myself better: I passed Calculus and Analysis (I am from Italy, we usually learn those subjects together) with a very good grade, but I struggle to remember some basic stuff to series series or some techniques to solve differential equations. I am able to remember effectively things in short or medium periods of time, but I do not have a way to remember things in longer periods of time (years). I realized this today, during a lesson of Analytic Number Theory for undergraduates: we needed to use the classic series for $\log 2$, the harmonic alternating one, and I was not able to recall it. I have realized that this is a general problem for me in Math, but it is very clear in Calculus/Analysis.
Do you have any suggestions on how to overcome this problem? How can I study in order to remember better thing in Math (both theorems, their proofs and how to do exercises)? Thanks