This quote was originally said by Ed Macauley, basketball player from the St. Louis Hawks (now the Atlanta Hawks) and it was what inspired Bill Bradley to practice more than almost anyone else in the league at the time.
"When you're not practicing, someone somewhere is. And when the two of you meet, given roughly equal ability, he will win."
The idea of practicing/working hard is important not just in sports, but in any endeavor in which you want to excel. In the context of work, your career, or your hobby, if you want to succeed you have to be willing to put in the extra effort to beat out your opposition.
Maybe it's skipping happy hour to stay late and catch up on a project, maybe it's going the extra mile for a client or boss, or maybe it's going to a coffeeshop every night to study instead of watching TV. You're putting yourself in the best position to succeed when it counts.
I know that personally, the thought that someone else might win ("And when the two of you meet, given roughly equal ability, he will win") makes me even more determined to do the work needed. I don't want to lose because of lack of effort.
This hard work adds up and pays off down the road when you're the one picked to lead the project, when you get a promotion, when your piece was chosen, when your business takes off, or when you land the coveted job or position everyone else was hoping for. Remember if you don't want to be great, someone else does and is making it happen everyday - edging you out.
When you feel yourself getting lazy, think again about the quote. Now, get out there and put in the hard work.