As women, when we get married we take on a new last name, the name of our husband. Doing this signifies that we are leaving behind our old self and becoming his wife and companion. It says to the world that we are now to be thought of in conjunction with our husband because we are no longer a single entity.
When we take upon us the name of Christ it is very similar to this. We are setting aside all the other names and titles we may be known by to take on His name and be known as His. We separate ourselves from all other things and are hopefully seen and thought of as being a "Christian."
As with a mortal marriage, a relationship with Christ takes a lot of hard work. It doesn't come easy and it doesn't always come naturally. Hopefully we've had good examples in our lives of others who have developed a deep and lasting relationship with Christ, but even if we're left on our own we can put forth the effort and learn how to make our "marriage" with Christ work. We have a big advantage over an earthly marriage in this relationship because we have the perfect partner- someone who is willing to listen, support, care, and love us no matter what. The only way that a "divorce" can happen with Christ is if we are the ones pursuing it. He won't give up on us.
In Mosiah 5:13 it mentions a man not knowing the master he hasn't served and I think this correlates pretty well with marriage too. I've been blessed to be born in a time and place where arranged marriages are not socially acceptable. I was allowed to choose for myself the man I would marry. If I had been told I was going to marry someone I had never met and didn't know it would be very difficult for me to feel any love or loyalty to that person. Possibly with time the feelings would come, but how could someone be close to my thoughts and heart if I didn't know even know him? The same can be said for our relationship with Christ. Is ours an arranged marriage? Have we gotten to know Christ and felt the desire to be "married" to Him because we already love Him? Or are we part of an arranged marriage where we are agreeeing to be His because it's what's expected of us?
The symbolism of marriage applies in so many ways to our relationship with Christ. As newlyweds with Christ we are often in that wonderful stage of discovery when everything is so new and exciting. We want to share our joy and our love of the Savior with everyone we meet. But as time goes by and we realize that this is a marriage and it takes a lot of hard work, we tend to do things with a little less enthusiasm. Our thoughts start to stray to other concerns and we find ourselves drifting from Him. Over time this can lead to separation from Christ. Or, if we are diligent and desire to have a lasting marriage with Him, we will recognize that the honeymoon period is over and decide to renew our commitment to Him and to His work.
In Mosiah 5:15 it also mentions that Christ will "seal (us) His" and I can't think of a better way to look at this whole concept of marriage to Christ than to correlate it with the symbolism of a temple marriage, or "sealing." If we are faithful to Him, "steadfast and immovable," He will seal us to Him just as we are sealed to our earthly spouses in the Temple, with no more worries about being separated. We will be on our way to becoming whole and one with Him, just as a husband and wife are "one" through marriage.