I think most players have that one piece of advice that they hold onto no matter what. My high school band director, Mr. Simmons died a few years ago. It was one of the saddest times of my life and I know he made many many lives better just by doing what he loved. He gave me the best advice I ever received. He always told me, "Practice does not make perfect, it makes permanent." If you practice something wrong, you will play it wrong. Always do your best and don't ignore even the easiest detail when practicing.