A Picture a Day:
No matter what job I have on my desk, since many years now I have had a specific personal rule. I must do an illustration by the end of the day. It can be anything from a simple black & white line-art to a finished color piece, as long as it is a finished image.
Sometimes I just go free on paper and draw the first thing that pop in my head, other times I might start with an idea and continue with it throughout the day. It's sort of an exercise of discipline if you will. And it helps me to get out of the monotony of some jobs. But also is an opportunity for me to study new techniques, try out new brushes, experiment with colors and so on.