Sketching will allow you to get better and to create more work faster in the short period of time, such as on your way home, or during a lunch break.
Consistency creates artists and builds the skills necessary.
Sketching is as important as working on big pieces. Or maybe even more important.
Your sketchbook should be a place where you can comfortably draw and ignore all of the potential possibility of judging yourself that your art is not good enough yet.