Raja Anwar’s The Tragedy of Afghanistan (Verso, London 1988) has this revealing quote:
In Afghanistan, settling a blood feud is an unemotional and impersonal act. It is like a sacred obligation which must be fulfilled. According to one Pashtun saying, ”˜a Pashtun curses himself for his hastiness even if the murder he has avenged took place a hundred years ago.’
(Thanks to Scott Burchill).