What you are as a single person, you will be as a married person, only to a greater degree. Any negative character trait will be intensified in a marriage relationship, because you will feel free to let your guard down -- that person has committed himself to you and you no longer have to worry about scaring him off.
When two people are under the influence of the most violent, most insane, most delusive, and most transient of passions, they are required to swear that they will remain in that excited, abnormal and exhausting continuously until death do them part.