I was just thinking about this the other day!
I have several projects that are ALMOST done, and for some reason I am reluctant to finish them. I finally decided it was because though I get that "Finished Object Rush" when I do complete a project, there is also a sense of "Okay.... now what?" Weird, isn't it? I think it is because we get so involved in the whole process of "making", that when we are done, there is kind of a momentary vacuum. Granted, there are always more projects, but for a moment there is an emptiness where your concentration has been. Your thoughts are used to going to that project, and now it is gone, and it could be a little mentally disconcerting.
Or, that all may be a bunch of psychological bunk.
Maybe I just procrastinate! LOL