Please don't try to write like Mozart. Good music doesn't flow out of you unless you're a genius. Rather, write like Bach in counterpoint. Write not what you want to write, but what you must. What produces a good work is not your current talent but the great rule of music. You may have to revise and revise like Beethoven or Bruckner, but you first have to teach yourself to be true to the logic of music.
Imagine a novice coming to a Karate Master. The novice says he's interested in how he can teach Karate to others. The Master reminds him that he's only learned Karate for a week and that he still doesn't know what Karate is. The novice says he already knows, but the Master says that the novice doesn't even know that he doesn't know Karate. "Your expression of 'How to teach Karate' is too vague," said the Master. "If you are to teach, you need to focus on a specific aspect of Karate first, like how to stand, or rather how to use your inner muscles when you stand, or even which inner muscle you should use in one way and which other inner muscle in another way when you stand. You don't know specific aspects of Karate yet. You just can't teach 'Karate' before you know and embody them yourself."