Quote Details: J. R. R. Tolkien: Nearly all marriages, even… – The Quotations Page
Nearly all marriages, even happy ones, are mistakes: in the sense that almost certainly (in a more perfect world, or even with a little more care in this very imperfect one) both partners might be found more suitable mates. But the real soul-mate is the one you are actually married to.
J. R. R. Tolkien, Letter to Michael Tolkien, March 1941
British scholar & fantasy novelist (1892 – 1973)
TimothyOne 
What if you are in an unhappy marriage? Since when is a fantasy novelist, a quotable authority on true soulmate relationships. For readers who would like some research, I suggest they read Divine Complement: The Spiritual Terrain of Soulmate Relationships.
Bless you,
Ariadne
I doubt that Tolkien would advocate being hasty to choosing a marriage companion, but then what would “even with a little more care in this very imperfect one” mean in practice?
I’m not sure I know exactly what Tolkien is getting at but I still thank God for the mistake of my marriage. In fact, I thank Him for all the mistakes that help me toward perfection.