I do exactly the same thing. So many projects I've finished to 80%, because I go...

I do exactly the same thing. So many projects I've finished to 80%, because I got the thing I set out to do achieved. That final 20% is documenting, finishing a UI, etc - and I'm not forcing myself to do (in my mind, the difficulty level) trivial, uninteresting things.

Hell, I probably wouldn't want to do those last things for money, either!