Marriage is a Vocation. It is a call from God to love another person as God loves; in good times and in bad, in sickness and in health; to love an honor another forever. Do you experience gratitude in your life for bringing you and your special friend together? Once you praise God for the gift of the other, it only makes sense that you ask the question; "Why? What is your plan for our union?" God has brought you together. You could have met and married many others had you been in different circumstances, but "No". This is the one the God has placed in your heart. Treasure her/him. Open your relationship to include God. God will give you the Grace in the Sacrament of Matrimony to love beyond what human love can grasp.
If you are wanting to prepare for marriage, see the priest six months previous to your planned wedding date.