Instead of ending the day with a completed project, end with a work-in-progress. In the morning you can get straight back into a painting rather than having to start from a blank canvas. You’re already out of the starting blocks rather than having to make the decisions that happen before painting (format, size, composition, colours, etc), and your subconscious will also have been working on it overnight.
We remember something unfinished or uncompleted better than the details of something that’s done; that’s the Zeigarnik Effect in simplistic terms. (It comes to us from the Russian psychologist Bluma Zeigarnik, who described it in her 1927 doctoral thesis.)
Read more: A Brief History of the To-Do List and the Psychology of Its Success from Brain Pickings.