A lot can be stored in a human brain, but if we stored everything in there, it would get too "crowded" very quickly and we would struggle to recall all the details correctly. This is also called "being frazzled" or simply overloaded, with in the worse case lots of content without context.

My recommended approach to a relaxed, efficient learning experience is to understand the broader picture of a topic, be able to analyse its patterns to break it down and study phrases and chunks to communicate within a given context. Language is a living thing. All the grammar theories in the world explained in the most effective way cannot outdo the efficiency of purpose-based study.