This is a bit prettier than my mental image. From WikiMedia by PJ NcNally.

Sometimes

Some days my mind is an empty cup

fine cracks through the glaze

a chip on the bottom

sound but worn

waiting to pour out on the page

but bone dry

so the page languishes

*

Sometimes my mind is a running engine

humming and churning

hot and full of sharp edges

waiting to be harnessed into a story

but uncontrolled

so the story churns, unwritten

*

Some days my mind is well behaved

full to the brim with thoughts

tires spooling neatly over asphalt

pages filling

story running

and it seems like it could never be

anything else

*

Sometimes is only

sometimes