Hi Julia,
Great topic! I think we all struggle with this, I certainly do and find myself feeling burned out and "brain frazzled" if I'm not careful. I found myself empathising with you (a good DT thing to do I guess).
I recently came across this Ted talk by Jason Fried
It is well spent 17 minutes (if you can fit it in without getting distracted 
). He talks about how working is very like sleep in that you need to go through certain phases in order to get to the important and most productive phase (e.g. deep, rejuvenating sleep or in the case or work "the zone"). Unfortunately most of us are either too interrupted or too distracted to every reach "the zone" of productivity.
Thanks for starting this discussion, I look forward to reading about other peoples methods to cope
Simon