Be purposeful about mastering your subconscious.
Yeah, writing in many ways is and always will remain a mystery. You don’t know why you love it; how you do it— you just do.
But the more purposefully you try to understand what goes on behind the locked doors in your mind where all the magic comes from, the better you’ll be able to control it.
So examine your work and examine yourself.
Discover why you write. Not just for Christ, or just because you have something to say— but what you are trying to say, and why. What was it that first sparked you? What common themes do all your works share? Heroism? Loss? Identity? Perseverance? Joy?
What flaws of your own bleed over into your writing life?
Identify your strengths; it will help you pinpoint and tackle your weaknesses.
Learn to recognize the symptoms of those weaknesses, then pull them apart and trace each flaw to its root.
Some things will always be mysteries. But the number of things that have to be is far fewer than most people think. The more you study yourself and your work, the more knowledge you have to apply to it.
That can only ever be a good thing.