I'm in the planning stage of a project larger than I've ever attempted before, a project on a scale that requires a hefty amount of planning. The thing is I've never done anywhere near as much planning for a previous project as this one needs, not even one tenth and probably closer to one hundredth.
My problem at the moment seems to be fatigue: I can get on and do up to an hour of good planning but then that's me basically spent for the rest of the day, no more productivity coming out of me. It's really annoying me how slow going it is. There is also a growing feeling of not doing anything and I've noticed that at times in the past when I'm not doing anything for weeks I get very down.
How do you combat planning fatigue, and what are your techniques for getting lots of planning done in a day?