I think it's the same problem I have, I often enter into projects due to a new idea or hardware application that grabs my imagination. What happens next is I learn everything (almost) there is to know about my new 'project' and after that is where the drive to finish tapers off.
What I have done is used the project to satisfy my brains need for stimulus (education).
Often I look at what will be the end result and realise that I'm going to end up with a bit of hardware or software or both that I'm not going to use
but the journey has been fun and engaging!
So to quote a cliche - It's the journey not the destination.

Having said that, I have a few projects that have been finished, although they too have had the definition of 'finished' altered at the end.
Ultimately I have come to the conclusion that this is not a bad thing. (Otherwise I'd be going nuts

)
- Rob.