Here's a problem they will never have at Toyota:
"What? You want me to build a Prius? Again? I can't, I just built one, so it's going to take a while until I even remotely understand what a Prius is anymore; I need some time out from everything Prius related. How about a Corolla, instead?"
The "cooling down" stage is a very important element in my creative process. For example, I may have some new idea that I've sung in a distracted moment, and found "hey, this would suit well in song X". So, when composition time comes, I fire up my gear, wear my beloved magenta Beethoven wig (just kidding), and start to let the old and new ideas mingle, and see if there's some chemistry there.
But after some time of such joyful process, I need to close everything and not think about it for a long time. I've completely lost my capability of judgement about the new developments of the song, and usually I reach out for anything else to do with the desperation of a drowning man, full of nervous energy (I once even started cleaning dishes, for god's sake...)
Such lack of judgment has played tricks on me in the past, and it can happen on both senses; I can leave the works of a song depressed by its awfulness, and then find while relistening later that my head starts spontaneously to bang -the ultimate quality test for me-. Surprises the other way round (ending the session with a feeling of triumph, but finding it only meh later) also happen.
The lightning rod analogy, one of my favorites, is of use here too; you've been conducting all that energy, and even if you have only been the conduct and not retained any, you don't remain the same, the iron must be cooled down, you need a rest.
This is perhaps the biggest obstacle towards applying one piece flow to song composition; distraction, doing other things, even multitasking, is a vital part of the process, and having several songs in the works at the same time, despite the many problems that increasing the amount of work in process causes, does help creativity; sometimes there is a funny game of synergies going on between the evolving songs: the way they "steal" things from one another... Since the night of times I've noticed that my songs have a tendency to come in pairs, a lot of them have a "brother" that is its complementary in some way; we used to joke about it in my former band...
I have a guitar and I'm gonna use it