Into the Wardrobe

While reading Listening to Lent by Robert C Hereth, a quote was mentioned by C S Lewis. The entire sentence reads "C. S. Lewis wrote that our sorrow now will be a measure of the joy we will know then, when in heaven heart shall find heart." Since it uses the word that it may mean it is not a direct quote from a Lewis book. Is anyone familiar with this and which C S Lewis writing it is from

How about this, from the Great Divorce: "They say of some temporal suffering, 'no future bliss can make up for it,' not knowing that Heaven, once attained, will work backwards and turn even that agony into a glory."