As then one who is crucified no longer has the power of moving or turning his limbs in any direction as he pleases, so we also ought to affix our wishes and desires -- not in accordance with what is pleasant and delightful to us now, but in accordance with the law of the Lord, where it constrains us.
In getting married, people surrender the power of moving or turning their limbs, and more generally their wills, in any direction as they please.
Abba Pinufius goes on to observe that literal crucifixion takes one's mind off the desires and cares that fill the lives of others. So too should marriage make worthless to the married many of the goods of the world they valued when they were single.
And there's that whole "till death" part, too.
Which calls to mind St. Catherine of Siena's prayer of praise that Jesus was fixed to the cross, not by nails, but by love. When you stop loving your spouse, when your will is no longer bound to your mutual good, you free yourself from the cross you freely chose. (Which might sound good, except that you will then find yourself on a cross of objective truth -- viz, that you're really and truly married, even if you no longer want to be -- and if you try to buck that cross you can lose a lot more than your life.)
Baptism and Holy Orders are similarly crucifixions; could we say the same about the other Sacraments?