You don't get to 'keep your word' when you never had the right to give that word in the first place.
Madness string 85973
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.