You loose interest... as you should! Because you are not interested in that, and therefore shouldn't spend time on it. What you are interested in is making the music you want. If your music already sounds how you want, you don't need to learn any theory, or to get bored reading about the theory of how to write like Mozart. If you feel your music still isn't coming out the way you want, then you need to learn the RIGHT KIND of theory, in order to fix that. People are recommending transcribing stuff you love, which can offer some insights. But it's hard to derive the hidden rules that are making the piece sound the way that it does, even when you transcribe it, or even have the score itself in your hands. Reading a novel -- seeing all the words in front of you, in plain sight -- does not teach you how to write a great novel. Because there are hidden things going on, like character development, plot design, all kinds of stuff... Hence storytelling theory to the rescue. Music is the same, there are many things going on that a beginner is unlikely to spot, even when looking at the score itself. If you are capable of deriving all the "rules" of the music you love from transcribing it or looking at the score, then awesome! Most people (myself included, when I first started looking at scores... wasted many years deriving mistaken assumptions from scores), need help with that. That help is: the right kind of theory.