Theatre Kid,
I realize this is an older post but I thought I'd add my two cents
I also have trouble with finishing things. I can't tell you the number of times I've started a project either work related or recreational only to loose interest and leave it lying in the dust.
It's so frustrating because I don't know what I have a legitimate interest in and what is just a passing fancy.
I'm beginning to think that the only way to really tackle this problem is with the help of a therapist or ADD coach.
It's so frustrating.