It is like fighting to build an empire, and the very people you fought for - the next generation - have walked in, burned it down, and shat in the streets.
This is something that a lot of people don't get. You and I were 100% justified in what we did, but it doesn't change how we feel about it. The burden of knowing we could pretty easily kill someone. The knowledge that we've hurt someone irreparably. That chunk it takes from your soul.