need to compare more and go slower

I love Harley Brown and I could only hope that this is similar to the way he works

So with observational drawing, as opposed to anything else, what would be the only thing you really need to use to know if you are being accurate with your drawing? answer- Measure and compare to what you are looking at. As a teacher, I am simply a new pair of eyes for you but the best thing I can do for you is to give you little tools for creating some kind of objective source of critique for yourself. So, try this: Rapid eye movement back and forth between the reference and your drawing. Look at one feature at a time. Or one area at a time. quickly back and forth. Look for the differences. Train your eye to see what's off. When you see the differences yourself, you will be unstoppable.

You just need to find the spot in front of the model where the tip of the nose exactly meets the cheek in 3/4 angle. Put tape on floor and after each break you just repose the model so the nose always touches the same spot on cheek. This is how we always did it in school.

Glad you are willing to try it. If you were exhausted you were doing it right.