You shouldn't take advantage of people with memory problems
Warren's friend Jack paid him back after borrowing money, but forgot and tried to pay him back again a week later.
Warren wants to respond to Jack's offer of money.
Warren lets Jack know that he'd already paid him back last week.
Warren takes Jack's money and keeps quiet about how he'd already been paid back.
Jack laughs at his forgetfulness and pockets his money.
Jack overpays Warren and has to crunch his budget to pay his rent.