The Kite Runner Chapters 22-23

"What we deserve" Has three means. First, for Amir, it means he received punishment from Assef instead of Hassan. "What was so funny was that,..., I'd been looking forward to this. ... Healed at last."(p.289)
Second, for Assef, he also received punishment from Sohrab for what he did toward Hassan and Sohrab.
Finally, they tried to end their battle. Assef said on page 42-43, "This doesn't end today, believe me. This isn't the end for you either, Amir. Someday, I'll make you face me one on one." They did what Assef said.
I agree with him because got satisfied, he healed from that and, as a result, he could saved Sohrab, and Amir was alive.