Listening to Experts
The benefits and difficulties in talking to successful writers are often the same as speaking with experts in any field.
The benefits are many and sometimes seem miraculous. Certain things that are wrong just jump right out to them. They can zero in on concrete problems and solutions; sometimes changing "a" to "the" changes your writing world. They can share that they, too, receive rejections and experience anxiety. They can help you brush off unimportant crazy-making things and guide you to the core.
The difficulties are frustrating, often both for you and for them. There are approaches they cannot recall not knowing, there are processes they have stopped using years ago because they did not find them either useful or necessary for them, they have tacit or instinctive knowledge about certain aspects of their work so they can't communicate it to others.