For starters, see Rich Hickey's talk on "Hammock-Driven Development" for more on the "background mind" (http://blip.tv/clojure/hammock-driven-development-4475586), and then see how what Dan Pink is saying about motivation (http://www.ted.com/talks/dan_pink_on_motivation.html) and what Sebastian Deterding is saying about gamification (http://www.youtube.com/watch?v=7ZGCPap7GkY) all connect into what Cleese is saying about creativity.
It takes the closed mode to focus on 'divide and conquer' and implementation of the idea as envisioned. This doesn't stop you going back in to Open mode to frequently consider where you are. Judge your work against it's initial goal etc.
If you are perpetually in Open mode you would continually add new features and extend the brief and never implement anything. I've worked with those kinds of people, they are a PITA.... although very creative.
Some people seamlessly switch between open and closed and others are stuck in one or the other.
I personally struggle to get in to the Open mode. After 30 years of disciplined coding, leading teams and divide and conquer my mind is highly specialised. It doesn't mean I'm not creative but it takes me longer to get in to that mode of thinking.
I wasn't stressed, thinking about deadlines, or worrying about whether my system would work or not. I was simply playing, with no goals in mind other than improve the "beauty" of the system. It was very similar to what I experience when I'm painting or composing music.
There was another system I developed a few months back - again, exclusively on my own time. I would only work on it while in open mode. Only once I felt my "art" was complete did I present it to my manager and a few execs. They loved it! My system has now replaced the old system and is now part of a real product. Had I instead tried to develop the system at work, because my boss said I had to, I highly doubt it would have turned out as good as it did.
I watched this last week, and this was my big takeaway. Programmers too often want to argue about what is right.
