The Straight-A Conspiracy book (don't ask me why ).
It contains great learning advice for students and contains one subchapter about "automaticity".
When you encounter something new you learn it and create a weak neural path in you brain.
You strenghten this path by training - the solution finding process becomes automatic - a neural path in your brain becomes a multi-lane highway.
What was then difficult and new - now becomes obvious and serves as a building block for higher level skills learning process.
For example you need to "feel" hex and binary math to easily "compute" subnet addresses and masks.