Check out Freeman Pattersons book "Photography and the Art of Seeing".
You know the "rules" of composition, which can get you on the right track, but once you get the camera up to your eye you are just arranging lines, shapes, colors, forms, and textures. With your eye to the viewfinder make you eye go out of focus, and just arrange the elements of design; pay attention to the visual weight of things and how they change as you move things around the frame. Try getting down low to change the perspective. Include something in the foreground, decide how much of the frame you want the foreground to occupy and then experiment with different focal lenths which will make the foreground occupy more or less of the frame. Once you know how to manipulate things in the frame it's just a matter of using the rules of composition to get your composition started and then trusting your gut on what really does look good. Relax, take your time, and allow you vision to evolve as you shoot.