I have kept a just-for-me catch-all notebook for over 20 years or so. In my mind, the pages lined up edge to edge would wrap around my entire life twice at least, but in reality they fit in a few boxes, with all the books from the past decade fitting nicely on a shelf in my studio area.
I rarely look back through them. Maybe once or twice a year I'll think of something and go digging for a note or a sketch. They're not very juicy. It's lots of lists, looping lines, things I didn't want to forget that don't matter anymore. I tape in receipts and business cards. I stick my stickers. And there are some paintings and little sketches that later grew up into something more. I make a pocket in the back cover for any loose notes.
But despite being full of brain clutter, they have made me into a creative person. These notebooks are the foundation of my art: the steady interface that holds up the warm and inviting place over the dirt and groundwater below.