Staring at a blank page in a new sketchbook is intimidating. Despite my best efforts, I tend to worry about whether a drawing will be "good enough" to merit being put into a notebook and as a result shy away from putting pen to paper.
To overcome this mental hurdle, I've started a new notebook that's intended for experimentation. And when I use this notebook, I open to a page at random before I start sketching to prevent myself from thinking about how a drawing will look next to the other things in the notebook.
Worst case scenario, I draw something that I don't like. By using pages at random, I'm less likely to see it the next time I open my notebook. And best case scenario, I've helped myself flush out an idea that I may have lost otherwise.