Beneath this reasoning, however, lies the very large assumption that we are working to create an illusion that supports the narrative content of the painting.
What if there is no narrative? What if we let go of the responsibility of making a convincing feeling of space or light, and the shapes are only shapes, the brushstrokes only brushstrokes?
It's asking a lot to expect that we can see our way clearly enough to apply the paint with total confidence when we are intent on telling a particular story. There are so many ways to go astray, how could it not be intimidating?
It could be that by sidestepping the need to "get it right" once in a while we can have the experience of performing a confident experiment. From what I've been seeing, this leads to bold brushwork and gorgeous paint. Surely some of the confidence that comes from having much less at stake will eventually carry over to the next "serious" painting.
The one part I'm not quite sure of is whether you can come back whenever you want once you've gone down the rabbit hole.
For homework, make a painting without erasing, scrubbing out, covering up or otherwise disguising mistakes. If you're confident that you can put the paint down and leave it alone in a realist image, my hat's off to you. But if content restrains your brushwork, try stepping into the territory of pure form.
If it's not fun, you're doing it wrong.