To what extent do you consider Okonkwo's downfall to have been brought about by his own pride and fears?
While Okonkwo does end up taking his own life, the question of his personal responsibility for this particular fate is a complex and interesting one.
Achebe’s protagonist certainly possesses some character flaws that lead to a variety of setbacks and punishments and drive his son away, but to answer the question of Okonkwo’s responsibility for his downfall, we have to look at the specific nature of that downfall.
To inform an answer to this question, we might pause to consider what may have happened to Okonkwo if the British had never come to Umuofia and the Igbo region. His chances of losing Nwoye seem vastly increased when the Christians come offering an alternative life for the boy. And Okonkwo's ultimate act of murder seems to be almost entirely generated by the circumstances created by the British arrival (as missionaries and as government/municipal agents, too).
If we can find some reason to think that Okonkwo’s fate would have been different if the British never came, then we need to qualify any responsibility we place on Okonkwo individually for his downfall. In other words, if Okonkwo’s downfall is partially the result of a British occupation, Okonkwo’s downfall is not solely of his own making.
Again, Okonkwo has flaws. He is incapable of showing any emotion but fear. Internally he is deeply afraid of showing weakness lest he appear to be weak like his father, Unoka. Okonkwo is also quick to anger. All of these traits eventuate into transgressions as Okonkwo kills Ikemefuna (when he does not need to), breaks the peace of the Week of Peace, and drives his son Nwoye away from the family.
In this last example we have perhaps the best rationale for arguing that Okonkwo is responsible for his downfall, because the loss of Nwoye is part of the general loss of cultural integrity that Okonkwo (violently) resists and that essentially defines his doom.
Were Okonkwo a different man, he could have nurtured Nwoye at least enough to keep him in the family. But, having driven his son away, protagonist Okonkwo speeds on the dissolution of his community. It is this very dissolution that he wants to fight against.
Okonkwo nearly recognizes this notion after his last encounter with Nwoye, gazing into the fire and brooding on what has come to pass.
“Suppose when he died all his male children decided to follow Nwoye’s steps and abandon their ancestors? Okonkwo felt a cold shudder run through him at the terrible prospect, like the prospect of annihilation.”
The beginnings of this annihilation can be attributed in no small part to Okonkwo's emotional limitations and his insistence on shaping Nwoye into a certain kind of man.
Nwoye is driven away, in large part, because Okonkwo’s “whole life was dominated by fear, the fear of failure and weakness,” and so he could not be kind or gentle or forgiving with a son who needed exactly these things.
Yet, without the significant presence of the British and the alternative life they offered to Okonkwo’s son, there seems good reason to presume that Okonkwo’s fate could have been different.
His fear and his pride do certainly contribute to the breaking apart of his family unit. His unyielding nature causes him to contribute to the dissolution of his community identity and community integrity in this way.
In the end, though, we also have to wonder if his pride and fear were entirely unfounded and absolutely negative and therefore should be seen only as weaknesses in his character. They are weaknesses, in some contexts and instances, but they are strengths in others. If the British effectively created a context where these traits became weaknesses, should we blame Okonkwo solely for his downfall?
I presume that you are talking about Okonkwo, the protagonist of Chinua Achebe's Things Fall Apart, and how his own fears and his immense pride contribute to his eventual downfall. Okonkwo's issues stem largely from his pride and his inability to be flexible in the face of the great changes that sweep over his village due to the pervasive influence of colonial forces. Okonkwo lives by and exemplifies exaggerated traditional tribal values that become antiquated in a postcolonial Nigeria. He desires to be a strong, dominant warrior, and he fears being perceived as weak and feminine. He values masculinity to the point in which it becomes detrimental for his life and well being. He is incapable of changing; Okonkwo is too proud to adapt to his changing environment, and this eventually leads to his downfall.