This kind of reminds me of some of the art classes I used to take - we had life drawing and a couple of the students had trouble deciphering exactly where lines should fall. One chick in particular drew our model as if he had a giraffe neck and she was certain that she was concentrating on how long his neck was and still couldn't make it look right on paper. Over time she got better and better at seeing where lines were supposed to fall, but it took practice. I think - as many people have said so far - it would be better if you concentrated on actual objects and drew them on paper with pencils. Eventually you'll get to the stage where you feel confident that what you are drawing actually looks like a true representation of whatever still life you are drawing from. You could move onto using pens and drawing more quickly. Fluid movements with a sure and practiced hand gives life to drawings.
Basically, what I'm trying to say is - practice. Practice big stylee, 'cause you obviously have a good eye for colour, and you'll develop a style of your own as you go along,. But the most important thing is to make sure that you are capable of drawing things realistically before all else. So get a sketch pad and a range of hard and soft pencils and get your hands dirty.