A-ha! I knew it !

What a relief! I've been thinking I might be getting old......

Ever walk into a room with some purpose in mind only to completely
forget what that purpose was?
It turns out that doors themselves are to blame for those strange
memory lapses.

Psychologists at the University of Notre Dame have discovered that passing through a doorway triggers what's known as "Event Boundary" in the mind, separating one set  of thoughts and memories from the next.  Your brain files away the thoughts you had in the previous room and prepares a blank slate for the new locale.

          Thank goodness for studies like this.  It's not our age, it's the damn doors!