This seems to me to be a bit like saying "screw hammers, what you need are screwdrivers." There's a brilliant talk by John Cleese that floats around HN every 6 months or so on how to be creative; if you haven't seen it yet, and you're interested in such a topic, please please please watch it: http://vimeo.com/89936101 If you agree with Cleese's premise, I think it follows that what you need is motivation for the open…
Motivation is essential. Why else would anyone bother, except for either a driving need or a deep and abiding interest? It's what keep you going when you start to question if you really want to keep at it. But motivation on a daily basis comes and goes. Everyone who goes to the gym or runs know that.
Discipline is about pushing through when motivation flags. I disagree that discipline is only useful for "closed mode". Discipline can also help you with open mode by making you daydream and play with ideas rather than packing it in for the day. Many extremely creative people have a very set routine. A writer might have fixed hours for when they write, every single day, for instance.
In the end it's about using both motivation and discipline together.