Happy are they, who in the matter of marriage observe three rules. Marriage

  1. The first is to marry only in the Lord, and after prayer for God’s approval and blessing.
  2. The second is not to expect too much from their partners, and to remember that marriage is, after all, the union of two sinners, and not of two angels.
  3. The third rule is to strive first and foremost for one another’s sanctification. The more holy married people are, the happier they are. “Christ loved the Church, and gave Himself for it, that He might sanctify it.” (Eph 5:25-26)

Bishop J.C. Ryle in his Expository Thoughts on the Gospel of Mark.