When I receive payment from the gallery, I enter the date I received it and the amount of the payment. For direct sales, I add the buy's name and address. At year's end, I know how many paintings I've completed, and the number each gallery has sold. This makes it easy to calculate the number of paintings each gallery will probably need in the coming year. My experiences as an artist and in the business of art have taught me much.
Productive artists spend a lot of time alone in the studio.
I treat my workday as though I were commuting and working for someone else. Rarely will I take time from painting on weekdays to go out with friends - though I do see them on weekends. Keep abreast of the market. This doesn't mean you have to paint for the market, but do incorporate market savvy into what you love to paint. Know which subject matter, colors and sizes are selling, and which frames are in style.