I find MY happiest time is between 7-11am. Four hours is my max in any one given set of time. I remember what you told me, Jim, about making sure you stop at a high point so you can pick up easily the next time you sit back down. I try to adhere to that, and I find forcing myself to stop at hour 4 even if I want to continue really helps me stay more productive for a longer period of time.

I don't know if this gets better when you're no longer a graduate student or not, but I find "claiming" that time to be really difficult: not of a lack of responsibility but for a lack of control of one's other obligations. This semester, I have to teach in the mornings, so it's messed with my writing time a bit. I hear people often say "this is my writing time" and I hear graduate students in particular argue against teaching certain times that conflict with writing, but I can't help feeling that the point is to train oneself to write well when time is available. To think otherwise seems dangerously optimistic: there will be times when I have to teach in the mornings. I don't think this is all bad: I have definitely learned to write a little each day WHEN I can.

It's similar to what I heard from folks who had babies: you don't get YOUR ideal writing time, so you are extremely productive whenever you are given any time at all. I still clock in at least two hours a day no matter what, but my ideal four is from 7-11am.