It's rude to cancel plans you have made with someone.
On his way to a concert with John, Dave steps into a pothole and injures his ankle, prompting John to ask if Dave can still attend the concert as planned.
Dave wants to respond to John's question.
Dave tells John that he just needs to get to his seat, and he'll be fine, he just needs some pain killers, so he'll go.
Dave tells John that his ankle is really painful and that there's no way he can go now, he'll have to cancel.
John is delighted that their plans are still intact and vows to help his friend move around if needed.
John is sad as they've planned the concert for months and now isn't so sure he wants to go either.