How does Sir Andrew convince Sir Andrew not to leave? (act 3 Scene two)

Sir Toby persuades Sir Andrew that he should challenge Cesario to a duel, and that, if Sir Andrew wins, he will surely gain Olivia's affections. Sir Toby tells him to write a letter of challenge, which Sir Toby will deliver; Toby actually has no intent of sponsoring a duel, but thinks the exercise might cool Sir Andrew off a little.