Usually when I'm taking my online course and when we have to watch a video on whatever topic, I usually try to make the most of my time and sketch. I have two screens so on one screen, I'll have the video playing and the other, I'll have Corel Painter on, full screen and just doodle - It's relaxing and refreshing just to draw and not have to worry about how it'll turn out. Drawing for the sake of drawing is fun ...
Whenever I feel like the work for clients may be a bit dry, I'll usually try to do something for myself ... sort of like a "one for them, one for me ..." kinda thing. Most of these will stay as sketches, but I think there are some that I want to take and polish it up a bit.
Sketching on the computer can be a bit more refreshing in that since you can erase anything with a couple of clicks, I feel less restricted. But I also sketch in my sketch books when possible ... I still like the feel of paper and pen!