“Rejoice,” I pronounced to our church congregation. “It's a command. In fact it's a double command. Paul tells us, 'Rejoice always in the Lord; again I tell you, rejoice!'”
Probably I should not have been the one saying this. It was a bit like a politician urging his constituency to always be truthful.
But even in the Beatitudes where the Lord Jesus speaks of the blessedness of being poor, of mourning, of meekness and being persecuted, He concludes by telling us to rejoice.
In God's economy, the very things that we think will make us unhappy and cause us to feel that we are unblessed are exactly what He uses to put us in a situation where rejoicing is the only sensible thing to do.