'Only a very wise man at the end of his life could make a sound judgment concerning whom, amongst the total possible chances, he ought most profitably to have married! 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 have found more suitable mates. But the "real soul-mate" is the one you are actually married to. You really do very little choosing: life and circumstance do most of it (though if there is a God these must be His instruments, or His appearances).'
JRR Tolkien in Humphrey Carpenter, The Letters of JRR Tolkien, p.51.
