Overworking A Metaphor

"Guess what? I buried my bone again."

I get these brainwaves for a column -- usually when I'm on my yoag mat or out in the field. My thoughts are rockin', the column is coming together, my point is brilliant but when I sit down at my computer and start to type,
it all turns to thick, sloppy mud. 
My brain goes swampy and I can't seem to dredge up the brilliance that occurred before I started staring at a blank white page.
Some columns flow out of me like the clear, rushing water of a woodland brook; others flow about as fast as trickle of sludge through a narrow culvert.
The column I'm working on for next week's newspaper is one of the sludgy ones; the ideas are stuck behind a blockage of wet leaves and twigs. At some point, rather soon, I'm going to take a big stick and poke away at the blockage. Once that crap is out of the way, the sludge will flow a little faster, more water will rush in and my muddy words will flow clean and clear. 
If not, I'll follow the dog out into the yard and dump all my words into a hole with her bone and bury them.
And that, my friends, is the classic mixed metaphor.