What is the main conflict in Requiem for a Dream: A Novel by Hubert Selby?

Harry and his mother, Sara Goldfarb, fight over his addiction to heroin. Sara lives alone in the apartment where she raised her son before her husband passed away. Harry lives with his friend Tyrone C. Love and it is common for the two of them to pawn Sara's TV for drug money. Harry and Tyrone spend their days hanging out with other friends who use various types of drugs, hustling just enough money to get by.