The question of how to know when a painting is finished, it’s one I have a hard time answering for myself. It’s a struggle to answer and do when you think a painting needs to be perfect, and you will always find things to keep improving.
When I finish that “last layer” of a painting, I take a break on that painting and focus on the next art project for a while. That break helps me create distance and detachment from the piece. Hopefully when I see it next time to know if that project is officially done, I’ll be more neutral when I ask myself the question if the painting is finished or not.
I try to be honest with myself by asking if I have given it all I could. If there aren’t areas that bother me because I notice a big flaw. It’s a balance to know when you can improve it for the best, or if you did everything you could but still good enough to share with the world.
In reality, a piece of art, whether is a painting or something in the written format, it will never be finished because each person that interacts with it will continue it. It’s part of the process that is out of your hands and it opens wonderful scenarios to be a part of.