I have learned to think about writing in terms of the flywheel (thanks to Tim and Johnny and Annie Dillard). I'm probably going to butcher this because I am still learning exactly how it works, but a flywheel is basically a gear used to keep the momentum going. Once they are moving, they contain energy that can be transfer into work. An old car engine, for example, had a flywheel in it. The starter turned the flywheel, which allowed to motor to run on it's own. This is why it's better to let a car idle than to keep turning it off and on. It takes more effort to start and stop a car, which is this economy means more gas, and we don't want none of that! The flywheel builds up inertia, which makes it resistant to change, which is what you want when you are trying to keep a machine moving. It takes more effort to start a flywheel from a dead stop than it does to maintain the momentum once it has started.
Feel free to correct me on this, but I think my point is right. When it comes time for me to write a sermon, it is like starting a flywheel from a dead stop. And cranking a sermon flywheel from a dead stop every month or so takes a great deal of intentionality. This is part of the reason why I speak at other places outside my church, like the Kansas City Rescue Mission. It is an easy way for me to stay disciplined in my sermon writing. Usually these sermons are short, fifteen minute reflections so they don't take nearly as much time. By the time you get in there, read the passage, and pray, your looking at about twelve minutes, and that's if the guys don't heckle you or try to answer every rhetorical question you ask, which is also part of the reason why I love preaching there.
I warned you these were meandering thoughts on (sermon) writing. Perhaps it's best to let someone more wise and seasoned in the art of writing to have the last word:
"Every morning you climb several flights of stairs, enter your study, open the French doors, and slide your desk and chair out into the middle of the air. The desk and chair float thirty feet from the ground, between the crowns of maple trees. The furniture is in place; you go back for your thermos of coffee. Then, wincing, you step out again through the French doors and sit down on the chair and look over the desktop. You can see clear to the river from here in winter. You pour yourself a cup of coffee.Birds fly under your chair. In spring, when the leaves open in the maples' crowns, your view stops in the treetops just beyond the desk; yellow warblers hiss and whisper on the high twigs, and catch flies. Get to work. Your work is to keep cranking the flywheel that turns the gears that spin the belt in the engine of belief that keeps you and your desk in midair." - Annie Dillard, The Writing Life, 10ff