You only need a 93 to get an A.

As a card carrying perfectionist, I tend to have difficulty with closure.  Since I want everything to be perfect I fall into the trap of thinking that I need to keep working in order to produce a result that I can be proud of, even when I have already done a terrific job.

Perhaps it's because when I brought home a 98 on a test, my mother always asked me - what happened to the other two points?

But, time has shown that I am the one who relishes perfection in an imperfect world.

That's where the concept of diminishing returns comes in.  Simply put, in every project you reach a tipping point.  From that point on more work yields fewer rewards.  So, you should wrap things up and move on.  The trick of course recognizing when you have reached that point.  Easier said than done.

But when I began teaching, I realized something significant.  You don't need to be perfect to be excellent.  You only need a 93 to get an A.  ;-)