Here is an example how you can lose the painting that you want make, when you work too long at it.
Left you see the first stage, after about 3/4 of an hour. Size 50x60, all in acrylic.
It was pretty vivid. I should have redone the part under the nose, reworked the chin, and suggested the shoulders. And leave it at that.
But I kept on painting for another half hour, and totally spoiled it. It's not even very bad, but it lacks the vivid paintstrokes of the first one.
I wish I could say that I learned my lesson, but to be honest, it's difficult to find that good spot.
I know I have to pay attention constantly.