Exercise: Find a picture. Make a sketch of it, or rather three sketches, in 20, 15 and 10 minutes. Well, I did. The question is: How well did I do?
I do see that while I concentrated on different parts each time, I also got more secure in my lines. Even if I didn’t get all the measures correct each time … but if I did this exercise several more times, I’m sure the difference between the sketches would be larger.