"The Fly in the Ointment" is a 1978 short story by V.S. Pritchett.
Harold, a professor of low standing, visits his father, who has recently become bankrupt. Although his father is contemptuous of Harold's low pay and status, he attempts to remain happy in his son's eyes; he does not want to seem a failure, but instead to be content with whatever he has accomplished. Although he has lost his business, he can now live a quiet, simple life, without the "curse" of earning more and more money hanging over his head. When a fly enters the room, the father focuses his concealed anger on it, and stands on the table to kill it, but cannot reach the ceiling. He abruptly becomes tired and allows Harold to help him down, and confesses that he has wasted his life chasing money. Harold, feeling shame and sympathy for catching his father in this moment of weakness, offers to lend him money to help him restart his business. His father, after making sure the offer is real, begins to adopt the businessman's personality again, and berates Harold for not offering the money sooner.
Pritchett draws on his own life for this tale, and weaves matters of parental approval, lust for money, dueling personalities, and parent/child respect into the story.