>>23862156From the few things i have learned when i was into drawing stuff:while learning to draw realism you need to observe and practice from the very source -nature- and not from an image. Light and shade in nature works in a three-dimensional way (of course) and you will notice it when you get a chance to compare your nature-based drawing to the image-based one.
VERY important thing to learn is observe how things actually look and not try to reconstruct the concept of the things from your head (at least at this point). For example you would want to ask yourself things like: should this line be strong like that? Is it really how this is shaped? Is this place supposed to be kept white or is the a shade falling at the surface when i look twice? You would maybe often think things don't look that well if you try and follow what you see as much as possible. But that shouldn't discourage you, since you are learning to see things in a different way. Keep practicing the new perspective and it will all shape out over time, i guarantee it.
Another equally crucial thing to remember is not to be afraid to experiment with how you are going to draw lines and represent light/shade to create a form. A stronger or lighter press of pencil on paper from a different angle can drastically change the way something looks. Try out different kinds of pencils, carbon, whatever that can create a line on paper or a different surface and compare.
I kind of lost the track of what i was writing and i don't know how much of it you know already, so i will end quickly with something im sure you heard million times:practice, practice, practice and appreciate every second of it, since it will be a step closer to the perfection you are pursuing. It is really the only way and remember that every single one that makes the art you admire was a beginner at some point and got to that level in the same way as everyone. I hope this will be somewhat helpful.