I rotate through these for everything from physical training to career goals to reminding myself to do my best to not be a douchebag:
“If I give up now, I’m going to regret it.” -Monkey D. Luffy
"Where's the future? Right here. Whose life is this? Mine. What are you gonna do with it? Live it by any means necessary." -Jefferson Pierce
"If you wanna stop this, then stand up! Because I've got one thing to say to you! Never forget who you want to become!" -Shoto Todoroki
"Waste no more time arguing what a good man should be. Be one." -Marcus Aurelius
"Giving help that's not asked for is what makes a true hero." -Izuku Midoriya
“I’ve set myself to become the King of the Pirates… and if I die trying… then at least I tried.” -Monkey D. Luffy
"If every porkchop were perfect, we wouldn't have hot dogs." -Steven Universe
Cal: "You're indeed brave Scout Trooper, but the fight is mine."
Scout Trooper: "Ohh, had enough eh?!"
Cal: "What? Look, you stupid buckethead, you're stuck in a wall!"
Scout Trooper: "Just a flesh wound!"