The brain is a very impressive tool, if you realize, you learned through practice, because as you were overcoming your fear that things would come out, you were improving your ability and gaining confidence, and I think that is the point with all things in life, to improve with practice.

Regarding why you forget things, it is simple: when we do or repeat certain tasks or things, the synapse in our neurons cools (science supports this, there are studies in this regard verified) doing our ability to remember things is forgotten and having greater predisposition to it. That is why scientists recommend leaving the comfort zone and challenging our brain constantly trying new things, new enigmas, different things, because in this way we will absorb more quickly knowledge, since synapse is activated when our brain finds new challenges, allowing this that we can have the ability to memorize.

Curious truth? Our human body is an impressive, complex machine that does not stop astonishing me.