Not that I am an "amazing artist" nor can I draw to save my life anymore
I used to draw all the time and have taken quite a few courses for drawing.
Anyway, even if you aren't looking to draw realistic things you should practice drawing them anyway. Just flip open a magazine and try to draw something from it.
Drawing is almost all right brained and our left brain creates sorts of stock images of what we think things should look like. For example you have an image for a person in your left brain inventory, but when you draw it, it turns out like a stick figure and your left brain says "good job, you did it!" but it isn't quite what you wanted. So you have to turn off your left brain to create what you are seeing in your imagination. There are a few ways to do this, so back to the magazine..flip it upside down and then draw the picture. This allows you to see the image for what it really is and not attach a label to it therefore triggering your left brain to take over.
Another good exercise is to draw a random squiggly line, then fold your paper and try to mirror it. This will help immensely with your symmetry.
To help with your proportions you could try placing two items side by side that are of different sizes and drawing them exactly as they are. Also get a mirror and try drawing your face, it doesn't have to look perfect with shading and all that, but just make sure the distance from your eyes to your nose and mouth is proportionate.
Basically, if you want to learn to draw anything you should start with real objects. This will help you with everything from realistic proportions to shadows and highlights as well as developing your hand eye coordination and spatial sense.
Hope this helps!
'Little spider weaves a wispy web, stumblin' through the woods it catches to my head. She crawls behind my ear and whispers secrets. Dragonfly whiz by and sings now teach it.'