As a photographer, I like to focus on "seeing" what's around me. As I take my daily walks (outside when the weather cooperates), I enjoy paying close attention to what I can see.
Sometimes something just catches my eye & I examine it further. Sometimes I actively seek out something interesting along my path. I encourage you to do this and I believe you will find it adds greatly to the relaxation of your walk. Notice all the sounds around you. Notice the patterns, color, lighting.