I guess my question is what is the sacrament - if the marriage as such or only the life-long bondage of marriage.
Canon law for the Latin Rite says in canons 1055 to 1060:
Can. 1055 §1. The matrimonial covenant, by which a man and a woman establish between themselves a partnership of the whole of life and which is ordered by its nature to the good of the spouses and the procreation and education of offspring, has been raised by Christ the Lord to the dignity of a sacrament between the baptized.
§2. For this reason, a valid matrimonial contract cannot exist between the baptized without it being by that fact a sacrament.
Can. 1056 The essential properties of marriage are unity and indissolubility, which in Christian marriage obtain a special firmness by reason of the sacrament.
Can. 1057 §1. The consent of the parties, legitimately manifested between persons qualified by law, makes marriage; no human power is able to supply this consent.
§2. Matrimonial consent is an act of the will by which a man and a woman mutually give and accept each other through an irrevocable covenant in order to establish marriage.
Can. 1058 All persons who are not prohibited by law can contract marriage.
Can. 1059 Even if only one party is Catholic, the marriage of Catholics is governed not only by divine law but also by canon law, without prejudice to the competence of civil authority concerning the merely civil effects of the same marriage.
Can. 1060 Marriage possesses the favor of law; therefore, in a case of doubt, the validity of a marriage must be upheld until the contrary is proven.
There are other canons going on to 1165 also related to marriage. The guts of it here is that the consent of the parties makes marriage, that such consent is an act of will, and that it is an irrevocable covenant. So valid marriages don't cease because people get tired of being married. If the consent was flawed in the first place one can say that there never was a valid covenant between them. That's why Catholics do not accept divorce but can recognize an invalid and null marriage because it never was a real covenant between them.
Because if we say the marriage was not real from the beginning, then it seems to have various serious repercussions.
It's serious business. But then so is a 'real' marriage that ends in divorce, even more so. Marriage has sign value, that of the sign of fidelity between Christ and His Church. Can Jesus Christ divorce his Church?