The definition of bring someone down is:
(phrasal verb) to depress someone
Man: Happy 25th anniversary, honey!
Woman: You too, dear! I love you!
Man: I don’t want to bring you down, but I want a divorce!
The bad weather brought the people down when it started to rain during the outdoor festival.
That boring old man keeps bringing everybody down by telling stories about the past!
Stop singing that sad song! You’re bringing me down!