Why is it ironic that okonkwo now blames his chi for his losses, especially the "tragedy of his first son"?

Chi means one's own destiny. It is ironic because not so long before the incidents Okonkwo was saying that one could control one's destiny. And now as the things did not work as planned, he started blaming destiny instead of blaming himself for the tragedy of his first son. This is clearly stating that first statement is contrary to second statement of this.