Nude no.3 with fixes, after seeing it with fresh eyes

When is a piece of art finished? What is the right time to stop and don't "overdo" it? I usually try to stop as early as possible, as I feel there's something really personal and alive in rough sketches and part of it is lost when the picture gets stiffer and gets too much details. But sometimes you just know that something is still missing (contrast in this case) and you continue from where you left and hope the best that you won't ruin it. This time, I think, I succeeded and the end result is a bit better than yesterday. Lucky me.