About a year ago I wrote:
I’ve accepted long ago that my mind latches onto ideas with a terrible grip and it’s inevitable that something that I’m currently spending time on will overwhelm my concentration, to the detriment of all other tasks and thoughts.
I’m starting to realise that I can predict when this will happen. It usually happens when there’s a natural lull in my work, such as the time just after completing a paper or finishing off some code. In the quiet time when my brain starts asking and wondering “What’s next?” I’ll queue up a bunch of possibilities and regardless of the order of their priority there’ll sometimes be one that simply overruns my thoughts. I’ll be able to picture in detail the stages of the task and exactly how to get started and an urge to get working on it; generally I find that there’s no point resisting at this stage and I’d better drop everything to focus on this one thing.
If I don’t drop everything (and attempt to work on what is most important rather than what is most motivating) I’ll generally start drifting into the fun work anyway, in and out of work hours, and it’ll slowly take over; in the meantime, I’ll have been attempting to multitask between a motivated task and an unmotivated one and generally not been as useful as if I’d concentrated on the former alone.
(Of course, there’s always the backlog that accrues during a time of blinkered/focussed working and it’s never fun to sort that out after emerging for breathe. Still, it’s often from the backlog that the ideas for what’s next? emerge.)
I think that learning how to transition continually between these focussed tasks is really the goal of productive work. It’s the dead time in between that’s soul-killing, when you finish a week or a month or a season and ask yourself “What have I been doing all this time?”.