At my great age of 61, or as my ma in law would say... Nearly 70, my mind goes completely blank on occasion. Names of things and people momentarily escape me. I think that your brain gets so crammed with info that it occasionally crashes, as a computer would.
Could maybe do with a brain defrag.
I don't think that I need to retain intricate power station details of plant that was demolished in the 90s. But I do....
Similarly, do I need to know how to gap cam/bucket shim sizes for a Dolomite Sprint head with a micrometre? Or rebuild an SU HS6 carb.... Fit big ends to a Ford Crossflow, Fit and gap CB points...etc etc ...can still do it....Duh. Do I need to? Nah....
It will be all right in the end. If it isn't all right yet, then it is not yet the end..