List common feedback from readers.
What comments do you get the most?
Remember, negative feedback isn't against you personally and doesn't mean you're a bad writer. It means you are growing as a writer and every comment helps you improve.
Keep track of what people like about your story
These are your strong suits and are good to keep track of what your audience likes.
They also help you keep going on days when you feel down.
Plus, they are great for marketing and "what people are saying" blurbs.
List of specific things you need to improve upon.
Such as using the same word too many times.
Or not adequately describing the scene.
Or dialog that feels more like exposition than a realistic conversation.