My deeply-loving relationship with my wife @katie, to use a perhaps predictable and personal example, does not endure because it is certain.  Every day we deal with uncertainty, in fact, as we face deteriorating physical condition that leaves us with sometimes precious few moments and minutes together.  We do not find that relationship because we are in complete accordance with each other, like some sort of clones, forged from the same mould or in some other way identical, but because we love and encourage each others differences.  There is perhaps no better demonstration of the folly of human vanity than true love.