To stop the this brain activity several tricks have been applied:
1. Turn the picture upside down
Turning the picture upside down confuses your brain and makes it harder to see those object-chunks. You only want to draw the lines, the objects are the end-result of their combination.
2. Work in a frame
A frame guides your pen when you draw the picture. It shows you how near the border certain lines begin and end. It also provides you with a steady reference for the angled lines. And lastly it limits the area of your focus, making it easier to concentrate on everything inside, marking everything outside as irrelevant.
3. Segment the object
To even further confuse your brain, segment the object into horizontal or vertical stripes. This makes it even easier to draw the exact line as you now have shorter frames which make positioning of the lines easier. The exact angles easier to see and reproduce. And you won’t as readily try to make your own object-chunks, because all you see are lines.