Light is more than just illumination
Light is more than just something needed to make a photograph. The right light can make your images really come alive, whereas the wrong light can kill them. Although you definitely want to focus your attention on your subject and compose carefully to get the shots you want, you can greatly improve your photos if you are aware of what light is doing to both your subject and the rest of the picture. What often distinguishes really good photographs from all the rest is how light is used to capture the photograph.
To see the light (literally), you have to go beyond framing a subject in your viewfinder or LCD. You have to look at your scene in terms of
what the light is doing. Is the light making the subject easier to see, or does it obscure it? Does the light flatter your scene, or does it make it harsh and unappealing? Would your subject look better in another light? Is the light soft and diffused, or is it bright and intense? Does the light have a nice, warm golden glow, or maybe an unwanted colorcast?
Use the LCD on your camera to see what the light is doing to the picture as captured by the camera. When you do not have good light, consider ways in which you may improve it, or find another time to try again. The more you take advantage of quality light, the better your photos will be.