Here, I decided to try something, to improve my not-making-me-happy drawing skills. I would take a famous painting for maybe 1-2 minutes. Then I would try to scribble it down in anything from 1-10 minutes, just to see how much I would get right. I would then analyze my mistakes and compare with the original. Then I would repeat the process.
As I just started this, I cannot tell how it will turn out, but so far the insight for me was amazing.
For my first subject I picked the famous Rembrandt "Anatomy Class".