It's not right to lie.
Mario broke the bathroom mirror, and he was worried about what would happen to him.
Mario wants to minimize the trouble he gets in.
Mario is asked if he broke the mirror, and he admits he did.
Mario is asked if he broke the mirror, and he claims that he didn't.
Mario's parents decide to go easy on him for telling the truth.
Mario manage to lie his way out of trouble but now he has to deal with guilt.