I would like to mention a few concepts I keep in mind when I train. They help me to maintain my focus and move forward, regardless of how big the artistic challenge in front of me may be.
Hundreds and thousands of drawings need to be made before progress becomes apparent, so work faster!
You are NOT drawing a picture! Making a picture is the job of a camera or a copy machine.
Instead, you aim to describe what you see and feel: there is no right or wrong, only accurate or inaccurate to your own perception. Don't think good or bad, correct or wrong, instead think: how dark is a surface, what is its local color and the value of that color, what is its shape, how wide is the shape, how tall is it, what's its color, is it lit or is it in the dark (not the same as the first item on the list: how dark is a surface)?
Instead of using words to tell someone about what you see and believe, use lines and strokes. Writers use words, musicians use sound, artists use lines, shapes and colors.
Don't try to paint what you think the object looks like, instead describe it, tell yourself and others everything about it which you can observe and understand. What an object looks like is irrelevant and fleeting, what you understand about it is why you put pencil to paper.
Keep in mind that your art is always good, as long as you do everything you can to tell your story about what you see. The more you describe your thoughts, the more you show the impressions of what you see and feel, the better your art becomes.
Only you know what you see, only you can train yourself to see things with more clarity and deeper understanding, no art program or teacher can do it for you. Watch, draw, check if your drawing clearly and accurately describes what you see, correct, do it all over again. And again.
Currently I'm going through a book of anatomical studies by Michel Lauricella, called Morpho. Here are some of my studies from the book. I strongly recommend this book to anyone who wants to improve their understanding of artistic anatomy.