Then Almitra spoke again and said, And what of Marriage, master?
And he answered saying:
You were born together, and together you shall be forevermore.
You shall be together when the white wings of death scatter your days.
Aye, you shall be together even in the silent memory of God.
But let there be spaces in your togetherness,
And let the winds of the heavens dance between you.
Love one another, but make not a bond of love:
Let it rather be a moving sea between the shores of your souls.
Fill each other's cup but drink not from one cup.
Give one another of your bread but eat not from the same loaf
Sing and dance together and be joyous, but let each one of you be alone,
Even as the strings of a lute are alone though they quiver with the same music.
Give your hearts, but not into each other's keeping.
For only the hand of Life can contain your hearts.
And stand together yet not too near together:
The strings of a lute are actually in groups of two called  courses . They are two separate strings yet strum together to form their singular sound. Metaphorically, this line acknowledges both the strings as two people having individuality and togetherness for the sounds of marriage, and music of love. 

On Marriage