Answer:
The story "There's a Man in the Habit of Hitting Me on the Head with an Umbrella" can be understood from various different perspectives. Even though Sorrentino claims to not have written it as a symbol for anything, the narrative can be understood as a symbol of life itself.
The man with the umbrella is completely random and inescrutable. The man receiving the blows has no idea why he is the recepient, or what motivates the other man. His only option is to take the blows. This is similar to how we face hardships in life. We just have to accept that tragedy is sometimes random. Moreover, the protagonist eventually gets used to this situation, in the same way we can get used to any problem we have in life.