I'm 43 now so I just chalk it up to aging. I've always had a freakish memory up until the last three years or so. It's still better than most, but it isn't "Holy mackerel, how do you remember that?" anymore.
Actually, I have a very good memory. Blocking out harmful memories from the past is a known psychological coping mechanism. You may also be referring to brain fog, which affects memories during those episodes only.