I think the thing that finally brought me around is this fourth-hand anecdote I read on Penelope Trunk's excellent blog:
Here's a story I heard from Alexander Kjerulf, who was talking about David Bayles's book "Art & Fear: Observations on the Perils (and Rewards) of Artmaking":Reading this story finally made me see the conflict between my desire for perfection and my image of myself as a person who loves to learn.
A ceramics teacher announced on opening day that he was dividing the class into two groups. All those on the left side of the studio, he said, would be graded solely on the quantity of the work they produced. All those on the right would be graded solely on their works' quality.
His procedure was simple: On the final day of class he would bring in his bathroom scales and weigh the work of the quantity group; 50 pound of pots rated an A, 40 pounds a B, and so on. Those being graded on quality, however, needed to produce only one pot -- albeit a perfect one -- to get an A.
At grading time, the works with the highest quality were all produced by the group being graded for quantity.
It seems that while the quantity group was busily churning out piles of work -- and learning from their mistakes -- the quality group had sat theorizing about perfection, and in the end had little more to show for their efforts than grandiose theories and a pile of clay.
Think about this in your own life, even if you're not using clay. The more you practice, the better you'll get. But you can't practice if you think only of perfection. Practice is about making mistakes; perfection comes from imperfection.
Believing that you can make something perfect now is believing that you will never improve. If you are constantly learning, your absolute best work now will be half as good as your average work later. Think of everything as a learning opportunity and you'll be excited to finish it and take on the next challenge.
If you can get it under control, meticulousness is a great quality to have. It can go from being something that holds you back and slows you down to being the steam engine that powers you to do great work. It's just a question of learning to recognize the right times to let it loose, and which tasks to aim it at.