I am a firm believer in the fact that anyone can learn to draw because I have no particular natural "talent" for drawing, and yet I have managed, slowly, over the last five years, to learn how to do it. Just in the span of the time since I created this blog, I have managed to improve pretty mightily (frankly I am kind of amazed myself since drawing is probably my most neglected hobby).
So if you are an aspiring artist and frustrated with your inability to draw hands or feet or relatively believable anatomy, just keep at it. Do the work! Copy images out of books, draw from life, use Google image search to find poses to help you. Study animation techniques (you will learn more about dynamic drawing from animation than you will from a straight anatomy text).
If you just keep doing it, and pay attention to what it is you are doing (i.e. learn how the body works under your skin), easier free-hand composition will gradually come to you! Hang in there!
The picture above are the bases for my final bodies. I haven't quite assigned heads to the poses yet but these will eventually be Lewis, James, and Morse. The fourth body might be Mish and I am drawing a fifth for Razi-el.