Too Good to Finish?

I have a lot of unfinished art projects cluttering my life.  Unlike other people who give up on a project because it is not turning out as well as they had hoped, I give up on projects that have come out quite well.  The fact is, the happier I am with my art, the more likely I am to leave it unfinished.  Why?  Because I am paralyzed by the thought that my effort cannot measure up to what I have already done. I might ruin it in the process of finishing it!