It's bad to not honor your end of an agreement.
Brian promised his friend Ted to help him with his math homework tonight but just got invited to a party.
Brian wants to attend the party.
Brian spends an hour helping Ted and then heads over to the party.
Brian skips out on his agreement to help Ted in favor of attending the party.
Ted is grateful to Brian, understands the math much better and is able to finish his homework.
Ted is disappointed and upset that his friend let him down and is unable to finish his homework on time.