Very often, the feeling of being wrong with each other is not mutual. One partner may never even thinks the other is having these feelings, and often shocked when confronted. In situations like this, communication was amiss somewhere between them; I think communication is one of the most important avenues that link one and other, and provides valuable feedback, so that we know how we are doing. Of course we are talking about sincerity and truefulness here. If honesty is not even there, the problem is far worse and no amount of communication can resolve. Being frank and honest is the basis of meaningful communications.
When all else fails, and they are no long able to have the feelings that pulled them together initially, I think people should part gracefully with dignity; It would be torturous for both to hang in there without reason to, and we really need to respect the other's feelings.
Waiting for the streetcar - NEX-6 & Schneider-Kreuznach Retina-Tele-Xenar 135mm f4 DKL