The only event on earth that causes joy in heaven among the angels of God is the conversion of a sinner which is facilitated by the preaching of the gospel. This is the only event on Earth the angels are all the time waiting for its occurrence (cons. Lk. 15:10; 1Pet. 1:12).
Any believer or minister who knows the ministry of the angels towards believers and ministers will love to make them happy always (cons. Isa. 6:5-7; Dan. 8:15-16; Zech. 3:1-7; Heb. 1:13-14).
When last did heaven rejoice because someone repented at your preaching?