There is no guarantee at all. Somebody can win, somebody can loose. Sometimes it seems that you dated and married two different persons. But there is a simple explanation of that situation. You just were infatuated by love during dating and didn’t want to see your partner’s cons. Or, maybe, you were bent to justify them. And you start to wise up after wedding. Take off your pink glasses and analyze your partner to minimize such situation. If nothing changes in your perception, it means that your elect is right choice. But if you start hesitating, please, think twice about marriage with that person.