I do not believe that you can marry the "wrong person." I am a great believer that life is pre-ordained and meaningful, and thus we are destined to be with the one person who completes us.
Nothing is as destructive to a marriage than the belief that our life choices are accidental, that the people who come into our sphere are coincidental, or that life is capricious and unplanned. To think this way means that we are all interchangeable, that any one relationship is just like another, and that a marriage is not really worth working for.
On the other hand, a feeling of predestination, that you were meant to be before you ever actually were, is the belief that gives us the stamina and will to make a marriage work. The belief itself becomes a self-fulfilling prophecy. Our mate is not like a garment worthy of exchange. On the contrary, they are ours and meant to be ours and worth the work that it takes to keep them ours.
The secret to love is this: You can make it happen. Love is an acquired taste, like wine or classical music. For example, I never enjoyed drinking red wine. But I wanted to learn to appreciate it. I took the time to recognize its variations and subtleties. That simple decision--that I wanted to like it--allowed me to become aware of the riches that it held for me. Take a similar approach to your marriage. Accept the challenge of learning to treasure the person you're married to. You will find that this person holds great riches that you never suspected were there.
In regards to this "other person": With cars and with people, it is always easier to fall for a new model. Like a new car, they are free of the scratches, the paint chips, and the little dents that characterize the old model we have been driving around for the past several years. But cars are meant to be traded in; husbands are not.
Marriage is a commitment. If you do not invest fully and completely in that commitment, you are cheating your marriage. By even considering the idea of a life with this "other person," you are undermining the vows you made.
As long as you keep looking for that newer model, you will never be content. You are probably quick to respond, "But I wasn't looking! This person just appeared in my life." Even if you didn't think you were actively looking, simply by responding to the stimulus of this other person, you are, in essence, actively looking. You will be distracted, your mind will be focused on impressing another rather than impressing your husband, and there will be no reason to try to fix the problems that are troubling your marriage right now.
Decide to commit, Regretful. Decide to discover why it is you are with the person you are with. Decide to rediscover your spouse, rather than discover a new mate. Decide to be happy.