Drawing of an apple in pencil

My mentor advised me that to hone my skills I should focus on desin. Specifically by reproducing the form of one specific subject and by exhaustive study and repetition to find the essence of that subject. After many many attempts I began to understand that I should not merely reproduce the apple but SEE it, understand everything about it, it's biology and nature, and process it in my mind, then was I able to create it on the paper.
It was a long and painful process but I learned so much from this.