#1, if you mess up on a painting, it is far better to wipe it off than to keep on trying to fix it. Things tend to get bigger as you fix them - like the lid and spout on my coffee pot.
So then I went back to grisaille to triple check my perspective and values. It turned out pretty well! And I learned rule #2 - worn out children's socks are great rags for wiping off your palette.
Back to color, I have learned steadfast rule #3 - don't paint if you're going to get impatient. You'll be more likely to keep painting over and over something and then you end up in that vicious cycle you started with - making too big and repainting. So I'm stopping here, even though I can see numerous touch-ups. I'll make them at a later date when I don't have such a burning desire to paint something else.