Complications in Marraige Vs Dating

So when you are in a relationship, a dating relationship, are your deepest and darkest secrets just supposed to come spilling out of you? I mean, I always hear about married couples having to work at their relationships (to keep them close, not necessarily to keep them from falling apart -like preventive action), but do you have to do that for dating also? If you have to do that for dating, is it not worth it? I mean, should the perfect couple be fine and just always magically "click" at all times before marriage and only after the wedding have to try to feel comfortable about talking about certain things... gosh, I have no clue what things I am even referring to... I guess I am just wondering how much dynamics of a relationship do/should change after a wedding. I mean, are there certain things that, if they occur while you are dating, are a bad sign, but naturally come up during marriage? Logically, it would seem that if they come up during marriage, they should come up while you are dating and not doom the relationship...