The belief that he controls his own destiny is of central importance to Okwonko. Later, several events occur to undermine this belief, and Okwonko is embittered by the experience. As often happens with tragedy, the catastrophe comes through a complex mix of external forces and the character's choices. Masculinity is one of Okwonko's obsessions, and he defines masculinity quite narrowly. For him, any kind of tenderness is a sign of weakness and effeminacy.
Male power lies in authority and brute force.
But throughout the novel, we are shown men with more sophisticated understanding of masculinity. Okwonko's harshness drives Nwoye away from the family and into the arms of the new religion. For all of his desire to be strong, Okwonko is haunted by fear. He is profoundly afraid of failure, and he is afraid of being considered weak. This fear drives him to rashness, and in the end contributes to his death.