What doing quick sketches does is free you up so much. Very often, we have an idea in our head, we get to the canvas or paper and think "I'm going to paint the best painting ever!" What happens nexts is we get tight and careful. We go away, practice every little aspect of the painting and then realize that our studies are better than the final product!
One lady in my art class comes into each work without an image in her head, and everything she does is an experiment. Everything comes out beautifully.
I need to learn not to srtive for perfection, goal setting or aims. I just need to just do and just be.