I can remember my husband's army serial number , but not what I had for breakfast this morning.
(That would be WW2.....)
Oh, that’s an easy one. It’s a matter of priority. To you, his Army serial number was very important to memorize; to keep in “memory” vs. “disk”, in computer terms. Right?
What you had for breakfast isn’t so important....so we sometimes reach a point where our brain can readily filter what’s important vs. what isn’t important.
Not a thing wrong with you. Still, that said, it’s never a bad idea to begin to exercise your short term memory. Lots of ways to do that. I even recommend games: dice games, dominoes (GREAT game for this), etc. Anything that exercises your short term memory.
As we age our long term memory remains sharp. It is our short term memory that we lose first. Also what you had for breakfast probably was not all that important, but you remember your husband’s serial number because for some reason it was important to you. I still remember my dad’s SSN because it was how I got anything done as an Air Force brat.