okay, so heres a tip for you to disregard completely. next time you want to practice your portraits or your anime or your doodles or whatever, put down the tablet and pick up a sharpie and some real live PAPER. DO NOT PICK UP THE PENCIL. DO NOT PICK UP THE ERASER. just draw, and dont worry about the mistakes.
see, when you use sharpie, if you mess up there isnt a whole lot you can do about it. you learn how to work with your mistakes, and this way you dont obsess over perfect angles and such. besides, it forces you to conquer a fear of the dark, which a lot of artist seem to suffer from.
i do a lot of drawings in sharpie (mostly portraits) and i think its really helped me. i suggest you try it!
one last things, most (well. okay, ALL) of my drawings are drawn from me looking at a photo of the person(s). some of these photos come from pictures on google, flickr, deviantart, magazines, etc, so comments like 'IVE SEEN THAT BEFORE' and 'I KNOW WHERE YOU GOT THAT FROM YOU POSERRRRRR' are not helpful! just FYI.
other comments, however, are always appreciated.