In The Dirt

The problem with writing for me is that I'm scared to death to start it. I have so many wonderful ideas, details and scenes playing through my head but when I sit down to begin the physical act of putting pen to paper, I balk.
The scene that immediately pops into my head plays out as follows:

A large beautiful bay stallion lopes along in a strong gait. As the animal gets to the jump and should be beginning his jump, he drops his whithers and locks his legs catapulting the immaculately dressed rider into the dirt. This is the beginning of my writing career.

So I'll start in the dirt.