Dietrich Bonhoeffer was a German theologian who was executed by the Nazis in 1945 for his part in a plot to assassinate Adolf Hitler. Here are three quotes on marriage from Letters and Papers from Prison.
It is not your love that sustains the marriage, but from now on, the marriage that sustains your love.
Just as it is the crown, and not merely the will to rule, that makes the king, so it is marriage, and not merely your love for each other, that joins you together in the sight of God and man.
God joins you together in marriage; it is His act, not yours. Do not confound your love for one another with God.