Study Study Study
Here's another two days' worth of 10-min studies from movie stills. A couple actually went over the 10 minutes by a little because my timer got messed up. I bet you can't guess what movie!
Studies don't have to be finished drawings...they don't even have to look good at all. The point is that you're focusing on one or two things, and isolating those thing. As soon as you start worrying about what the picture looks like (like I have to fight myself about) you impede your progress on the things you actually need to work on.
Just keep drawing, drawing, drawing!