That stops working once the code reach a certain size/complexity limit. It is a different limit for different people, but there is a point where there is just too many parts to be possible to fit in a head. There is also a middle stage where everything fits, but can't be accessed all at once but require some time to retrieve specifics when looking at areas not in recent memory. The middle step is more achievable the easier the code is to reason about by black boxing parts.
That stops working once the code reach a certain size/complexity limit. It is a different limit for different people, but there is a point where there is just too many parts to be possible to fit in a head. There is also a middle stage where everything fits, but can't be accessed all at once but require some time to retrieve specifics when looking at areas not in recent memory. The middle step is more achievable the easier the code is to reason about by black boxing parts.