The most important message I got from a cleaning blog, whose name escapes me right now, is that it's not important to finish a task. It is important that you improved your environment and that you didn't leave a bigger mess than you started with.
For example I'm folding clothes right now. Say I have 14 t-shirts. If I fold 10 and then get too tired - if I make sure to put the 10 folded t-shirts away, I have 1) made progress on the task of folding my clothes and 2) reduced the overall mess in the room.
Finding your own definition of "finished" on a sub-task and respecting your energy limits is much more helpful in the long run than declaring any task that isn't "complete" by some sort of outside definition as worthless. Because if you are completely unwilling to progress on (and take a break after) sub-tasks, it might mean that long or complex tasks are simply not doable.
