burst somebody'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!
See also: bubble, burst

ˌburst somebody’s ˈbubble

bring an end to somebody’s hopes, happiness, etc: Things are going really well for him. I just hope nothing happens to burst his bubble.
See also: bubble, burst