"If it's important you will find a way, if not you'll find an excuse."
"You're not training to be the best in the world, you're training to be the best in the world on your worst day." -Rhonda Rousey
"I hated every minute of training, but I said, 'Dont quit. Suffer now and live the rest of your life as a champion." - Muhammad Ali
Also, I believe there's one that goes "Champions aren't born, they're made."
Idk if this is a quote, but I've told myself it enough it seems like it.
Champions have heart.