This is taken from Ronda Rousey's book My Fight Your Fight
Aristotle said "We are what we repeatedly do. Excellence then is not an act, but a habit". Winning is a habit, and so is losing.
You can get into the habit of going into a tournament, a meeting, or an audition telling yourself: This is just for practice . If I fail, I can always try again later. If you go in with your excuses already laid out for you, it's hard to shake that mindset when "later" finally comes.
Or you can go into every endeavour with the attitude that you are... going to knock this one out of the park. You can tell yourself: I am bringing my A-game because that is the only grade of game that I have. I am here to win, and you can come along for the ride or you can get the hell out of the way.
Winning is a habit that means trying - and expecting- to be better than everybody in the world every day. (Ronda Rousey - book My Fight Your Fight)