The knowledge you are given in an initiatic teaching is so far removed from your usual field of consciousness that it does not penetrate your brain immediately. But the fact you have heard it or read it means something of it will remain in your subconscious, and one day, once your understanding has developed, this knowledge will resurface in your memory.
In order to reach this understanding more quickly, you must exercise your brain, which is the best instrument there is. It does not grow weak with age along with the other organs, for the divine hierarchies have deposited their powers in it. No, it doesn’t grow weak, but only provided we nourish it with mental activity. Thought is a sort of ladder we have received from cosmic Intelligence, and it is essential we learn to use it to go higher.