A couple months ago, I picked up the habit of drawing two note cards everyday. I use an app that tracks whether I complete this daily goal (among others) or not, and this gives me some reinforcement to keep it up. I've also been archiving these drawings on a secret Instagram account. This has helped me realize that not every drawing will be good, but that's ok. The main purpose is that it eventually becomes a lot easier to get started on something when you have to do it daily. You start to build up a new confidence rather quickly. What I like about working at a small scale is that it's almost impossible to overwork it. Even the more detailed note cards only take me about 15 minutes to finish. Simplicity is not easy for me, so this practice has helped me with that. The sketchbook drawing above is definitely more detailed, but it includes some of the characters born from the note cards.
There is also something to be said for doing purposeless art. I had a roommate in college who always asked me "what is that for?" when I was working on something. I would always tell him, "for myself." He would just look blankly at me. I might not have been the best student, but I really believe that keeping a sketchbook has helped me stay curious about art and about life. :)