Most people over the age of 35 years old will probably be able to agree with the statement that “you learn a lot of things in life, and you also forget a lot too”.
Things get replaced in your active memory as you move from phase to phase of your life, meet and lose people, as you change careers, take up new hobbies and interests.
For instance, I used to be able to speak German passably well, but this got replaced by Dutch, and now I don’t practice speaking Dutch at all, it’s faded from my skillset.
A lot of experiences cast shadows and are best totally forgotten. Others, which we consider valuable, we tend to summarise for ourselves and retain at least the outline of what we have known.