Do you find it’s easy to go from eight open windows to four, but that to go from four open windows to one it’s much harder?
Anything over six is clutter…
Between five and two is an environment that you have control over…
But the move from even two to one is much more difficult.
Having only one application open increases the friction of moving from one app the other. That has other consequences that just making app switching difficult, because with even a few windows open you can have a sense of control over multiple data outputs, but with only one application there is no “I have this, this, and this covered right now”.
The friction makes it harder for your focus move between contexts. You are making the trade off of split-attention and of multitasking for focus. It’s risky to make a decision to focus on just one thing and cutting yourself off of everything else, and there is a positive consequence of having a single application like WriteRoom open, because in that situation all you have is the application, and your focus.
When you make the tradeoff to remove your attention from other applications, you gain more focus. Focus is more uncomfortable than attention though, it’s a trickier thing to work with. With different applications open and your attention split, your focus enjoys the room it has to move around. Keeping a concentrated and still focus creates the discomfort.
Have you ever started writing an essay with the TV on and with chat open? And then have you felt that resistance to turning off the TV, and to turning off the chat, in order to focus on writing the essay?
When you remove the distractions and take away the exits for your focus to escape to, trying to get it still is at first difficult. Then, when there’s no escape or distraction to break your focus, when the external factors are removed, then it’s possible for you and your focus to connect real intimately with your work.
The You writing with IM open the TV on is not the same as the You who is focused.
WriteRoom: http://www.hogbaysoftware.com/products/writeroom
Ommwriter: http://www.ommwriter.com/
Open Mode 
Yes, yes and yes. I struggle with this ALL the time. Especially going from 10 windows to 5… I used to think I was a great multi-tasker, now I’m realizing I need to become a better focuser.