About what was Okonkwo grieving?literature
In many ways, Okonkwo towards the end of the novel is mourning the incredible humiliation that he and the entire village have suffered at the hands of both Enoch and the colonial powers.
Enoch had unmasked one of the egwugwu at the ceremony which, according to Igbo tradition, meant that the spirit had been killed and that the entire ceremony was jeopardized. Of course the fact that Enoch was from Umuofia and had some idea of what he was doing made this even more difficult.
So in many ways, Okonkwo is mourning the loss of their innocence and the integrity of their traditional way of life.