Here's a hypothetical question: who is more limited? the person who dies after a plain, ordinary life, having never really explored his potential - who with discipline and effort might have chosen to be a scientist or surgeon, or a lawyer or tennis pro, or a writer - possibly of successful novels? He couldn't bring himself to commit and follow through. Or is it the person who dies at the end of a long life of service and effort, who created several partially successful efforts but, let's face it - didn't have all that much talent and never really found the way to touch people with her art in ways that deeply reached them? Which one is more limited? The person who lived a long life but didn't have that much talent? or the one who died without having really taken many chances - you might say with a lot of life left to live? The person who died without actually having done anything could have been practically anything - the person who dies old and used up had to make many hard choices - pay her nickel and take her chances - but the jig is up and she accomplished nothing more than... she actually accomplished.
And if you are trying to answer this question about which one is more limited, I'll spare you any further doubt: being dead, they are both equally limited.
I think those of us who hate to finish do so because we secretly know we will be dissatisfied with what we create - however good - because it fails to meet some internal model, doesn't touch everybody, doesn't change them... or any criticism will do. If we start but do not finish, then the art (and I'm talking about more than art) can show promise and also never fall short. It allows us the luxury of having talent but spares us the cost of having that talent judged and found wanting. And often we are the harshest critics, of course.
In my opinion the solution to being unable to bring yourself to finish things is to finish them and to learn how to celebrate achievements in yourself as you would in others - not expecting perfection and universal impact - but recognizing that our limitations can also include the inability to see how others will be touched by what we have done. Let the work stand on its own two feet, not an expression of you or your psyche, but an act of creation.