The adult learner has a wealth of knowledge not just about the language they need to study, but about how their primary language functions. Most people aware of their learning style and what they need to know.
What most people lack is an awareness of how their brains can be supported in learning, or how to structure learning to maximise results.
The adult brain is a collection of connected information networks. Try this for yourself: when watching a TV show or reading a book, for ten seconds, consciously note and write down how you understood what you watched and heard. Then, draw a map of how those different perceptions connect to your real experiences.
In learning another language, we can consciously activate various networks such as word forms, paraphrasing, nuance and contextual usage which all activate connections.
With a little regular practice, these networks become chemically reinforced in the brain, resulting in new communicative skills.