In trying to learn more about graphic design and the structure of images, I thought drawing would help. And it has, I now have a better understanding of shadows, structure, texture and how to achieve these.
Another benefit of is that I find drawing therapeutic, its has a calming influence on me and the more I do and learn from books the more confident with images I become. The way I draw is in silence and if that's not possible with headphones on. Both letting me solely concentrate of the pencil and paper.
From the sketches below you can see how using darker and lighter shading gives the perception of depth and texture within the images.