You start your life by forgetting your past. All the times you fell over, were hungry or overtired, or shat your pants as a baby or toddler. You don’t remember that time unless something happened that’s traumatizing in the extreme. Somewhere between that age and when you start school you start retaining memories. Not all of them but enough to reminisce. You’re growing still so every day is a new experience and not everything makes the cut. And then you age. Once you cross 40 you’ll notice a lot more that you cannot remember why you went to the garage but you can remember all the teachers from your elementary school days. Most of your classmates too but that guy’s name in Accounting who you talk to every other day is nowhere to be found. And when you reach an age where death is becoming likely every day, you reminisce and you remember lots of stuff from ages ago but not what you had for breakfast. Dementia fucks with you but they remember their moody teenage music tastes and react more to that than their own offspring.

Memory retention is not a linear thing.