Don't try this at home...... When I got my 500L F4 IS. Yes, that was when I started to get better. How? I got interested in bird photography early on but very focal length limited. I was mainly shooting birds. As you can see, when you are focal length and light limited, you can't apply many of the basic composition principles. The bokeh? Forget it. I had to fake it in photoshop since a 400L 5.6 + 1.4x converter does not produce good bokeh.
When I began to shoot with the 500L, I was like someone shooting people portraits with a 50mm lens. My subjects were birds of course. I was able to apply many of the basic composition principles. I was able to read the lights and position myself accordingly.
Another break thru is public aquarium photography. I haven't seen many good works so far. When I learned about exposing to the ambient light with - stops exposure compensation and using the flash as the main light, I discovered that I can "freeze actions" in low light situation without using a ridiculous fast lens. And at 1/200s shutter speed.