When a man and woman marry, the two individuals then become one. This marvel of marriage implies both a new and tremendous liberty for them both and a vital and voluntary constraint upon them both.
On one hand, a tremendous liberty: two individuals working together in unity are able to accomplish and enjoy far more together than they ever could alone. Every good marriage is made up of more than just the sum of its two simple parts. Marriage multiplies the pleasures, the accomplishments, and the opportunities of life.
On the other hand, their new oneness implies restrictions — they are no longer free to make their own decisions or set their own goals as individuals, without consideration for each other. Go to any three-legged race and you will quickly see the awkwardness and bondage of two individuals, who are joined together, still trying to make their own way and rely on their own strength.
Although in our Western culture the decision to marry is made by the two individuals, once they commit themselves to the God-invented institution of marriage it is in effect God who has joined them together. They are therefore responsible to God for their commitment to each other.
What God has joined together in the holy bonds of matrimony is not to be lightly or selfishly or wrongly separated by any mere mortal. Therefore, strive to make yourselves, and those loved ones of yours who are married, more unified for the glory of God. Never seek to divide was God has glued together.–BBH