An idea from a video by artist and leather vest aficionado Stefan Baumann about keeping a "doodlebook" really hit home with me. It's a simple enough concept: keep a small sketchbook with you at all times and "doodle" in it without really focusing on it.
Here's the video:
It seems almost too simple to be valuable. But what Stefan said here was really important, about not being precious with your sketchbooks, roughing them up even, and people getting too caught up with the words "sketches" and "drawings", so much so that those materials end up sitting unused on a shelf because we're so concerned what we might put in them won't be masterpieces.
When you just look at as a "doodlebook", you don't get so caught up in second-guessing what your put in it, you just do. You don't really even need to show them to anyone because this is just for you, but I took some pics of my current doodlebook...
The other concept Stefan suggests is every five pages, use your non-dominant hand, seen above in the bottom right image. This has been REALLY challenging and an interesting exercise to stretch your abilities and ways you look at your art.
Having a doodlebook with me has helped me open my big sketchbooks that I've had for a long time and just start working in them instead of over-thinking and then paralysis setting in.
It's a tool that I think is definitely worth your time.
I also think it could valuable in the same way for writers. I recently suggested to my better half that she start carrying around a small notebook to write random thoughts and ideas down in throughout the day. It's only been a couple days, but she feels like it's helping get her creative juices flowing again.