I agree with tweety.
I also think that some people are definately not cut out for marriage. It doesn't make you a bad person, your personality just doesn't qualify you to be in that sort of a situation. And if that's the case, you need to realize that, and not string someone else along. And you surely shouldn't get married, because then your just screwing over the person your married to.
Also, a lot of people get in a marriage and convince themselves the grass is greener on the otherside. When in reality, everybody has their hangups and issues, and there is no such thing as the perfect person your always going to get along with. This isn't disney.