“There’s no such thing as a painless lesson, they just don’t exist. Sacrifices are necessary; you can’t gain anything without losing something first. Although, if you can endure that pain, and walk away from it you’ll find that you now have a heart strong enough to overcome any obstacle. Yea, a heart made fullmetal.”

“A lesson without pain is meaningless. That's because no one can gain without sacrificing something. But by enduring that pain and overcoming it, he shall obtain a powerful, unmatched heart. A fullmetal heart.”

“You cant gain something, without giving something in return”

“All right people, listen up! If you've got a family back home waiting for you or if you just want to save your own skin, turn around and walk away. Also, women! I have no intention of fighting any women!”

“Greed may not be good, but it’s not so bad either. You humans think greed is just for money or power, but everyone wants something they can’t have.”

“Humankind cannot gain something without first giving something in return. To obtain, something of equal value must be lost. This is Alchemy's First Law of Equivalent Exchange. In those days, we really believed that to be the world's one, and only, truth.”

“So that the new generation that will be born can enjoy happiness. To pay the cost we will have to shoulder corpses and cross a river of blood(Riza Hawkeye -- Fullmetal Alchemist)”