When is a painting finished?

Merrily Down the Stream 

Little Bear Creek (Original 2010) 

When is a painting really finished?  It's rare that I look at a painting and not see "just one more thing" that needs a few more touches.  More times than not, I have paintings sitting around my studio that are annoying, like a puzzle that the pieces won't fit... In my mind I know they will... I can "almost" see it.  I know it is close by but it is just beyond the horizon.... 

The original version of "Little Bear Creek" is one of those paintings? When I began working my goal was to go in the direction of pointillism but keeping the painting  looser.  Different elements never felt right, so a few days ago, I decided "Just quit thinking about it and do something" The starkness of the stream leading into the painting and the distant tree near the center were major issues. My final version is much more restful to my mind with the scattered pink wild flowers along the little creek bed. What an ahhh moment to get rid of that central tree!  Makes me wonder WHY did I ever put it there in in the first place???  I guess it is all part of the process.... finding a point to be at rest with your painting, while expressing the place you know to be just beyond the horizon....  Is this an issue you struggle with in your paintings?  What is your solution?