Thanks for a great challenge.
My "get up and go" just got up and went. (common colloquialism)
My energy has passed its expiration.
I'm running on empty.
My vim and vigor has vanished. (or "have", but I prefer singular)
My buoyancy has bottomed.
At this point the horizontal suits me over the vertical.
I have lost altitude. (airplane metaphor)
I'm beat.
I'm all washed out.
I'm done with, done away with, undone.