I once asked my wife to teach me to draw an Erlenmeyer flask. She showed me, and she's a good teacher. Then she said "Draw 50 of these. By the time you've done that, you should see how the lines work." She was wrong. My first flask was no worse nor better than the 50th one and I never did see how the lines worked.
I can do math, but my drawings look like I never graduated from Grade 1.
