Quote from : One Zentangle A Day: A 6-Week Course in Creative Drawing for Relaxation, Inspiration, and Fun Book

There are no mistakes in Zentangle, so there is no need for an eraser. If you do not like the look of a stroke you have made, it then becomes only an opportunity to create a new tangle, or transform it using an old trusty pattern. A Zentangle tile is meant to be a surprise that unfolds before the creator's eyes, one stroke at a time.