I think you have to be careful not to beat yourself up about it if you do have partially finished projects.
You probably did achieve something, like doing prototype tests on a bench to see if an idea works, or learning to lay out a circuit board - there is always something. It is not as good as a finished project I admit, but sometimes you get what you needed to get from a project, and there is no real point in finishing.
For me, the thing I dread is getting really unmotivated with a project at work. Sometimes it is me. Sometimes things happen outside my control that just totally kill all the momentum in the project.
I do admire it when I see someone who seems to have amazing abilities to get a project done quickly, without the slightest sign of a burnout. I remember at school reading "The Black Cloud" by the famous astronomer Fred Hoyle. In that someone, with about one night to spare, designed and built a computer out of box of valves that was able to learn and decipher and alien's language, and was able to perform real time bidirectional translations with no sign of an error. This allowed the heroes to tell the alien to rack off rather then destroying the Earth, and so the alien racked off.
I want to be able to invent, design, build and program a super computer with true artificial intelligence from scrap parts overnight too.
Richard