pianoloverus Passion for learning is good but I certainly don't agree with the title of this thread because it doesn't say anything about realistic expectations.
Going by the title would be the wrong way to go. There is a concept being developed in the story itself and that is what matters. What I see in the story is a point about manner of learning . The OP has self-knowledge, finding professionally, and now also in music, certain things create a lot of learning, and other things have the opposite effect. Applying the same thing to music, suddenly speed of learning, and interest, were greatly enhanced.
This also juxtaposes the statement by the fellow who wrote that book who simply dashed off opinions. In those opinions, speed of learning was determined only by age. The older you are, the slower you learn, being the idea. Speed of learning, effectiveness of actions, are determined by other things, especially the HOW of the matter. The gist of the message in the opening post is an important one. It is not directly contained in the title, except as an opposition to the other broad statement. There should be no broad statements.