One of my personal problems (and I have many) is that I like feeling like I'm making progress, so sometimes I will do things that only feel like progress, rather than achieving something real with my time. And sometimes I will stop a task halfway through, because that feels like enough progress, and tomorrow I can do the rest, and get that same feeling again. Finishing a task does hold some satisfaction, but that very same satisfaction is right there in the middle, too, as long as I can see I'm getting closer to the goal.
Mokalus of Borg
PS - So if progress is measurable, I'll stop halfway.
PPS - And if progress is not measurable, I'll stop as soon as I realise that.