For a marriage to be sacramental a number of aspects must come together. Each party must enter the marriage freely. No event, person or circumstance must be pressuring them to marry at this time. To marry only because a child in on the way is not to marry freely. To marry because you re getting older and chances for a match are fading is not to marry freely.
Persons trapped by some addictions are unable to be free enough to covenant a sacramental marriage.
Marriages must be undertaken with an unconditional nature. Pre-nuptial agreements that put ifs into the covenant are a stumbling block to sacramentality. Neither the man nor the woman may say that they will stay married only if the other remains faithful, or has a job, or stays handsome. They marry with no ifs, ands, or buts. In a sacramental marriage the couple promises to be faithful to each other for the rest of their lives.