[The Devil and his angels] have... persuad[ed]... humans that a curious, and usually short-lived, experience which they call "being in love" is the only respectable ground for marriage; that marriage can, and ought to, render this excitement permanent; and that a marriage which does not do so is no longer binding. This idea [comes from their] parody of an idea that came from [God]... Things are to be many, yet somehow also one. The good of one self is to be the good of another. This... He calls Love, and this... can be detected under all He does and even all He is... He introduces into matter... the organism, in which the parts are [set at odds with] their natural destiny of competition and made to cooperate... In... humans [God] has... associated affection between the parties with sexual desire. He has also made the offspring dependent on the parents and given the parents an impulse to support it-thus producing the Family, which is like the organism, [but] the members are more distinct, yet also united in a more conscious and responsible way... [Heavenly Father] described a married couple as "one flesh." He did not say "a happily married couple" or "a couple who married because they were in love"...
C.S. Lewis, The Screwtape Letters
cheating, divorce, family, love, marriage