I think it does have to do with courage. The reason inventive individuals have trouble keeping on one track is that they're afraid one of their other ideas is better, or that they'll otherwise miss out on some other opportunity elsewhere. The courage comes in saying "Damn it, I don't care what else is out there, I'm going to pick this one project, take it down the rabbit hole, and see where I come out, regardless of what else is out there."

I say this as someone very much like Aaron, with a long trail of half-finished projects and a couple that I actually saw through long enough to bring to fruition.