Ran out of motivation.
That's it: I'm done.
The Big Project and all the Little Projects have come to a halt because I lack any incentive to even work on them, much less finish them. It's not as though their conclusion would have improved my life in any way; none were for pay or to make my life easier. They were merely projects. The primary motivation for doing them was boredom, and now that isn't enough.
Maybe it's the change in the weather or maybe I've stopped caring that I'm bored but ... 'on the shelf they sit', and that's it.
It's a matter of 'wait-and-see if the situation changes'.
And after reading this you'll have a taste of just how bored I am. So bored that even the boredom is boring.