What's a response to this "never does the human soul appear so strong as when it forgoes revenge, and dares forgive an injury"?
It means that despite the wrong that has been done to you, if you can let go and forgive instead of seek revenge then you are a strong person.
does it need a response?
That says it all
A good response? "That's right."
its talking about a break up. And instead of trying to seek revenge on a broken heart, you learn to forgive and let go of the past.