burst someone's bubble
burst (one's) bubble
To bring someone back to reality, especially if they are dreaming or fantasizing about something unrealistic. Look, I hate to burst your bubble, but there is no way you're getting into Harvard! You're a C student!
burst someone's bubble
If someone or something bursts your bubble, they stop you being so happy or satisfied. A terrible defeat in Saturday's match burst their bubble. Costa burst her bubble, telling her that her boyfriend had been arrested.