Hiromu Arakawa

Enduring and forgiving are two different things. You must not forgive the cruelty of this world. It's our duty as human beings to be angry at injustice. But we must also endure it. Because someone must sever this chain of hatred.

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. Yeah, a heart made fullmetal.