You do not marry for companionship, support, wealth or comfort, and definitely not to change someone. As corny as it may sound, you marry only for love.
One might ask if love is enough to sustain a marriage and I have no doubt that it can. The reason for this would, I believe, be obvious: God is love. It is His presence that binds a man and a woman in marriage. Countless priests remind us at every wedding that to have a successful marriage, you have to have God at the center of your relationship; and that it takes three to have a successful marriage.
In my college days in the Ateneo, we were taught that love is not a feeling; that it is the affirmation, not the possession of another. That finds its ultimate expression in marriage. It is a conscious act, a decision made everyday, to love your spouse as God loves His Church, which simply means that you intend to let God in your marriage every single day, every hour, every minute, every second and every fleeting moment you have on earth.
To affirm the other is to make your wife the best version of her that she can ever be. You give everything you can even at the cost of your own life because that is the highest form of love: that you give your life for another in the same way that Jesus gave His life for us, even death on a cross. You do not have to worry about your self because your spouse has the same objective, and with the two of you consciously bringing God into your marriage, your marriage will endure any test and surpass every hardship.
To marry for any reason other than love is selfishness because it is only in loving that we are able to give freely of our selves and expect nothing in return.
The Bible tells us that in the end, we have faith, hope and love, and the greatest of these is love. It also tells us that the greatest commandment is to love: God first with all our heart, soul, mind and strentgh, then our neighbors as we love ourselves. Love then should rule our lives from how we treat our enemies to building lasting relationships in marriage. From how we treat sinners to serving our heavenly Father. In all these, there should always be love in our hearts. We exist because of love, and we live to love. Above all, love.