Alternate title: Responding to what you make, not what you intend
There is a big difference between what you want to do and what you do in each and every mark that you make.
I hear a lot of you say, well I didn't think of that because I was thinking about something else. This is often the case. Our minds get preoccupied with a goal and we forget to look at the piece as a whole, or really check and see what we've done.
This kind of tunnel vision is dangerous in art.
While it is nice to separate art into different components, the undersketch, sketch, ink, color, shadows, and atmosphere, they are never all that mutually exclusive. While working in each of these stages you still have to consider anatomy, composition, impression, concept, and all the little things in the composition guide. Once you take that into consideration then any one of these stages can be revisited at any time.
So what's the point of this post?
Awareness. When you place a mark down, on paper or on the screen it is never going to turn out 100% how you intended and with consideration to all the things listed above. What to do about this? After each mark, or a few seconds in an area if you insist, take time to really compare what you intended to do to what you did to the piece as a whole. As always, ask yourself specific questions: Is that really hair? Does that give the impression I intended?
Is this head the right size in comparison to that body, what about the eye? Consider, what does that color do to the composition? Is it too bright? Do the colors match?
After enough practice with this you'll be able to have your process be more about responding to what you have done rather than trying to pull something out of your head.
It will go fast fast fast eventually but you still must take time to look at what you have done and what this does to describe and what it does for your composition.
Sometimes it is nice to only consider shape for a while and try to describe a line, or a shadow... figuring out what questions are relevant where is a big part of the art process. You can never really forget about your intent.
An easy question to ask marks is "does this match my intent?" though a harder question can be "What is my intent?" but that's what the composition guide and concept are for. This becomes especially easy with copying exactly a reference, as your intent is to draw as you see. You learn to ask questions of proportion, angle, impression of yourself and really measure and compare, paying more attention to the reference and simply responding to how your work doesn't look like the reference.
Each mark you make can be a response to your intentions on all levels. From what shape you're working on to how this affects the shadows, the emotion, the textures, and all the compositional stuff. This takes time to craft and improve (and familiarity with your medium doesn't hurt either), but hopefully this awareness will help guide you on your way.
So now, you've made a mark and you consider it, but it doesn't do anything right. Time to correct. Use the last mark as a foundation, compare, ask yourself specific questions, ;but make it a conversation between yourself and the piece and be open to interpretation. For example: "Should it be shorter?" measure "... nope, longer." draw draw draw "Should it be rotated more this way or that?" ... "I dunno" draw this way "How about now?" consider whole "Nope, that way." draw draw draw
So, what to take from this?