Many relationships break down because of communication. The partners do not communicate their true feelings to each other. Not only that, they also assume that the other will understand what is in their mind. This is still more dangerous. Sometimes, a partner refuses to communicate his/her feelings and feels frustrated and cheated because of non-communication. The truth may be totally different.
Another reason of destruction is a change in attitude. For example, you believe that you and your partner are having similar opinions about a situation. One day you are shocked to find that your partner has changed opinions. You try to bring your partner back to his/her earlier state, but he/she refuses. Why people change is a mystery, but they do change with drastic results. They not only suffer themselves but also destroy the other person if the relationship is deep.
Are you unknowingly destroying your relationship, because you are ignorant about the real state? Have you kept all your communication channels open and does your partner share everything in his/her mind or do you find him/her brooding alone? As far as changing one's opinion is concerned, it becomes difficult to keep the relationship intact after that. The relationship was based on certain common views and once these disappear, the foundation shifts and the relationship crumbles. Let’s give an example. Both partners value honesty as the greatest value. Now when it comes to test, one of you turns back and says that there is no use of being honest. This u-turn will destroy the relationship, because both of you shared a common bond about honesty and it ran very deep.
Keeping a watch on the relationship is the best way to prevent destruction. Don't assume that everything will remain ok forever. Sometimes, they don't. In ignorance, one doesn't watch for the vital signs and is shocked when the day of destruction approaches.