Your sorrow shall be turned into joy. (John 16:20)
Their particular sorrow was the death and absence of their Lord, and it was turned into joy when He rose from the dead and showed Himself in their midst. All the sorrows of saints shall be thus transmuted, even the worst of them, which look as if they must forever remain fountains of bitterness.
Then the more sorrow, the more joy. If we have loads of sorrow, then the Lord's power will turn them into tons of joy. Then the bitterer the trouble the sweeter the pleasure: the swinging of the pendulum far to the left will cause it to go all the farther to the right. The remembrance of the grief shall heighten the flavor of the delight: we shall set the one in contrast with the other, and the brilliance of the diamond shall be the more clearly seen because of the black foil behind it.
Come, my heart, cheer up! In a little while I shall be as glad as I am now gloomy. Jesus tells me that by a heavenly alchemy my sorrow shall be turned into joy. I do not see how it is to be, but I believe it, and I begin to sing by way of anticipation. This depression of spirit is not for long; I shall soon be up among the happy ones who praise the Lord day and night, and there I shall sing of the mercy which delivered me out of great afflictions.