Dedication, and humility.
IMO every person who says they've just finished the perfect mix, or is "as good as they are ever going to get" is wrong.
To be better than everyone else, you have to realize that you aren't, and never will be, but pursue that ideal regardless.
Attention to detail, actually caring about what you are doing etc. are all not scientifically measurable quantities, however, I would argue that, along with talent, even though you might not be able to measure these things with numbers, I'd argue that you can hear them.