Just yesterday ...
.. I was doing some performance mods on a pair of speakers for a customer. I just finished one and ready for the second. Since these were "mirror imaged" speakers I made sure I had them set up correctly on the speakers stands and moved them into position. Grabbed the second speaker, put in on the bench, and c-a-r-e-f-u-l-l-y removed the screws mounting the woofer. (Woofer surrounds are very unforgiving when introduced to sharp tools). After extracting the woofer and removing the fiber fill, I realized this was the speaker l had just completed.
When the number of moving parts is reduced to TWO, and you still get it wrong, you must be getting old. (75 next month)