Self-thrown gauntlet

I have in mind a challenge to my wit:
To write each day a sonnet for to share.
My horse is shy, yet champing at the bit,
And feels a wish to canter in the air.

My metaphors are fond of running loose,
And though the fields are weeds I'll let them run
Into each other publicly to bruise
And wallow, dusty, earthy, for some fun.

Though precious be the form and meter, see
The trot and bolt of this my chosen mode,
And though no Spenser, Will, or Francis be
I, e'en lame horses sometimes can't be whoa-ed.

About all this I am quite serious.
I start now, with intention, furious.