I don't know about other painters, but I often paint many versions of a painting underneath the final layer. The painting may appear to be spontaneously done, but oftentimes, there are layers of false starts, frustration, and anguish underneath.
I thought it might be amusing to share with you the underlayers of "Abstracted Flowers II". Here they are:
With the next layer, I brought all those twigs together, but went overboard with the darkness. I started to paint in some white roses, but it was starting to feel too stiff and formal.
When things aren't working, I grab some vivid tubes of paint and pile it on. I have to smile when I see the difference between my first and final versions. I'm in love with color, so I should just follow my instincts in the first place. I'd save a lot of money on paint if I did.