I have been going to life-drawing classes for a while now and I see little to no improvement in my work. The classes are not classes per se, simply a group of people hiring a model and drawing from him/her.

So I decided to try and self-educate myself by copying old masters works. I picked up a book "Drawing Lessons from the Great Masters" by Hale (many of you know this book) and tried copying Jacopo da Pontormo's "Nude Boy Seated" (on page 39). I'm trying to analyse the drawing in front of me and get the character of the line, but the result is very poor. Sorry I don't include my picture--I don't have a camera.

I'm wondering if anyone could give me some advice or point me to useful resources on how I can tackle this issue. I beleive, there will be quite a few members here that faced and solved this problem. Tips, workflow suggestions, what should I look at, how to get the right mindset, any help would be much appreciated.