Playing in my traveler's notebook makes me happy. I love the flexibility of being able to bind different papers into each signature. The page on the left was created with acrylic paints and sharpie flip chart markers.
One of the ways I've changed my daily journal, is that I treat it more like a an actual travel journal, so have started including photos, ephemera, etc. in addition to to art play.
The thing about always have a journal and basic art supplies with me is that I can do quick 15 minutes watercolor sketches like the one above. My everyday carry supplies include some Derwent watercolor pencils, a pen, and a water brush. Light and portable.