When you sketch directly in pen the lines aren’t always put down exactly where you wanted. But because it’s ink, at some point you decide not to correct your lines and create muddiness, but instead you simply finish the sketch and accept the loss of likeness.
This isn’t a tragedy, it’s just part of the reality of practice. I actually like the process, because it gives me the immediate opportunity to make a study sketch (as I did here on the recto page). With such a sketch I can note the things that I want to change in order to get that likeness. I can reinforce my learning by pointing out where my eye is judging proportions incorrectly. I am using my editing eye to find specific things that I can fix in the future. I’m learning about my tendencies to go too wide! Something I call “wideology.”
For me the notes are as fun as the drawing.