John 16:21

A woman, when she is in labor, has sorrow, be cause her hour has come; but when the child is born, she no longer remembers the pain, for joy that a man is born into the world.

Revelation 7:14-17

And I said to him: Sir, thou knowest. And he said to me: These are they who have come out of great affliction, and 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
A woman, when she is in labor, has sorrow, be cause her hour has come; but when the child is born, she no longer remembers the pain, for joy that a man is born into the world.
Revelation 7:14
And I said to him: Sir, thou knowest. And he said to me: These are they who have come out of great affliction, and have washed their robes, and made them white in the blood of the Lamb.