John 16:21

When a woman is in labor she has sorrow, because her hour has come; but as soon as she gives birth to the child, she no longer remembers the anguish, for joy that a child has been born into the world.

Revelation 7:14-17

I said to him, "Sir, you know." And he said to me, "These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.

Treasury of Scripture Knowledge

Summary

Because thou shalt forget thy misery, and remember it as waters that pass away:

Bible References

Because

John 16:21
When a woman is in labor she has sorrow, because her hour has come; but as soon as she gives birth to the child, she no longer remembers the anguish, for joy that a child has been born into the world.
Revelation 7:14
I said to him, "Sir, you know." And he said to me, "These are they who have come out of the great tribulation; they have washed their robes and made them white in the blood of the Lamb.