I do read every review I receive, and take each with a grain of salt. The positive could be embellished and the negative could be overly critical. Whether I receive praise or not doesn't affect my attitude toward my work, but I do take every review in as neutral of a position as I can to learn what could be better with my work moving forward.
Literary success, to me, looks like publishing a book that someone loves. To be considered someone's favourite author would make all of my work worth it.
Reading and rereading current and past works. That second, third, or fourteenth read through of a work in progress or completed work helps to really drive home what works and what doesn't.
If it is someone's first book, I advise reading a great deal of successful and not so well-written books, and take what you can from each. Both ends of the spectrum offer advice.
If someone already has published works, keep reading. Educate and work on bettering yourself.