Call me old-fashioned, but "The feeling is gone." shouldn't be a deal-breaker.
If your relationship endures over time, you'll experience the whole range of unwanted emotions including anger, bitterness, jealousy, dissapointment and boredom. Marriage means keeping both feet in the relationship during the difficult times and bringing one's best self to the relationship even when (or, especially when) you don't feel like it.
I also hear, "I struggle more with my partner's personality than his behavior. If I don't like his (or her) personality, nothing can be done about that."
But personality is expressed through behavior. Personality isn't written in stone.
The introvert can make an effort to initiate conversation and connection. The "over-talker" can practice brevity and leaving more space. The disinterested partner can practice asking questions to his partner and listening with his whole heart. The "fix-it" partner can dial down the criticism, advise-giving and "I know-what's-best" attitude. The pursuer can call off the chase and put her energy into focusing on the quality and direction of her own life. The overfunctioner can learn to do less. The underfunctioner can learn to do more. The rigid partner can learn to bend like grass, and the overly-accomodating partner can learn to stand like an oak when something really matters. You get the idea. Be the one to change first, because waiting for the other person to change first is a recipe for relationship failure.
The longer I work with couples, the more I feel humble about predicting what's ahead. I know a couple where the husband's distance had a very eroding effect on the relationship. He was basically "missing in action" for more than a decade. His wife also disengaged from the relationship. Then the wife's mother became very ill and moved to the town where they lived. The husband stepped up to the plate in a spectacular way. He began to do a huge amount for his mother-in-law and was very supportive to his wife as she dealt with her mother's illness and ultimate death. She developed a newly found love and respect for him. Their marriage flourished.
I'm not suggesting that it's a good idea to sit like a bump on a log through long years of distance. I am saying that I've been around long enough to know that without a crystal ball (where did I put that thing?) I can't predict the future of relationships. Marriage (like life) takes many surprising and unexpected turns. It often takes only one person to turn things around.
To blame things on "the feeling is gone" or "personality" can be an excuse not to change. Our personalities are not as fixed as the stars and sure as sunrise. As I explain in THE DANCE OF ANGER and MARRIAGE RULES it is never too late to change our part in the "stuckness" that bring us pain. There are some very specific steps that one person can take to make things a while lot better.
The hardest thing is getting started. The second hardest thing is maintaining the change over time when you don't get quick "results." Change requires motivation, good will, and a genuine wish for a better relationship.The reassuring thing is that it sometimes takes only a small change on the part of one person to make things a whole lot better.