When you cannot put another stroke to it.

I must agree. I too find it hard to let a painting go as finished but I have come to terms. Now I try and set a very detailed image of what I want in the finished piece and when it is there I'm done. Or when I feel I have captured what is most important.

I ask myself: Sure that area could have more detail or maybe a little more time on this or that, but will it add to the overall image as a whole or is it just fussing over minor details?

Sometimes a painting is done long before I start. What I mean is due to poor planning it is doomed to failure and I should just start over with a fresh idea.

Well that is what I try to keep telling myself anyway. But I do find sometimes I just have to say done. Other times I just do a new painting if I am unhappy with how the first turned out instead of trying to fix the first one to death.

I really want my paintings to look as if I just whipped them out with loose brush strokes and not appear worked at. So often I have to start over to fix it for I just can't get the look I want if I don't get it the first time. I try to make the first brush strokes show though to the end in the finished piece. If I keep working and working a area that freshness is lost.