I'm sure I've said it before in one of my monthly posts, that I'm not a great painter, not even a particularly good one, but I do like my little travel watercolor set and enjoy using it in my journals. For me, it's more about taking the time to sit down and spend some time with a particular view, than painting something I'll want hanging on the wall. This isn't easy for me. In general, I tend to be a more detailed oriented person, so when faced with a gorgeous landscape, I have a hard time trying to focus on where to start, or what to include.
Someone along the way gave me a slide, with the center film popped out, and suggested I hold this up to a view, move it around, until I see the view in a pleasing composition and one that's easier to translate onto my page.
I find myself doing this for bigger vistas, as well as smaller details. I helps me keep things in better proportion to each other, as well as focus on what it is that I'm drawn to in a particular scene.
This little empty slide has become a fixture in my small set of supplies and I find I'm constantly pulling it out. You can also just use your hands in the same way, which will help you change the size too.