In order to understand why compatibility is important, we must first examine the psychological context in which any couple is embeded. We can view any couple as existing somewhere on a continuum of functioning, with healthy functioning on one end of the dimension, and unhealthy functioning on the other end of the continuum.
Healthy functioning is characterized by each person in the dyad having good self esteem, not having too much or too little to cope with, and viewing one another as need fulfilling, empathic to one's needs, and having one's best interests at heart. When this situation exists, communication tends to be effective and the relationship is characterized by a minimum of projection. Projection, for our purposes, is the belief that one's partner is intentionally withholding something that one wants or needs, or that one's partner is intentionally preventing one from doing something that would bring pleasure or fulfillment.
A couple begins to move towards the more unhealthy end of this dimension of functioning when stresses mount. Stress usually involves a requirement for change, and draws from one's psychological resources. Eventually, stress can contribute to a loss of self esteem and confidence. One begins to see the world as a less safe, less friendly place, and one begins to view challenges that in the past would contribute to one's feelings of mastery and competence now as something to be dreaded and avoided.
When this occurs, individuals who are experiencing a loss of self esteem are often unable to identify the cause of their dysphoric mood and declining confidence. They just know that something doesn't feel right. In their search to understand why they are feeling down, they often begin to view their partners as the source of their unhappiness. The partner is seen as withholding something needed or desired. When the individual buys into this belief, he or she is likely to withhold something from his or her partner. The partner may react to this by intentionally withholding, and the stage is set for an escalation of projection and withholding.
When couples arrive at the extreme unhealthy end of this dimension of functioning they are often ready for divorce or separation, or to enter marriage counseling. They are likely to view one another as unfeeling, uncaring, and nonsupportive. They have become increasingly self-sufficient and their ability to negotiate has become diminished. They are more likely to make decisions without considering how their decisions affect their partner. They are also more likely to attempt to coerce their partner into going along with their decisions, rather than attempting to negotiate and compromise.
What prevents couples from quickly sliding from the healthy to the unhealthy end of this dimension? Most importantly, each person must have faith that when he or she communicates his or her concerns that their concerns will be understood and taken seriously by their partner. In order to have this expectation, they need to have in place a similar way of communicating and resolving conflict. When a marital partner has lost faith in his or her abilility to communicate, and to be heard and taken seriously by his or her partner, he or she is more likely to attempt to ignore the initial red flags and to eventually fall into a pattern of withholding and projection.
The second quality of the relationship that helps to slow the slide from healthy to unhealthy functioning are the areas of similarity that minimize the potential for conflict and contribute to the overall intimacy in the relationship. These areas of similarity contribute in their own unique ways to the overall harmony, stability and adaptability of the relationship.
The third quality of the relationship that helps to prevent a rapid movement towards reactivity, projection and isolation is the overall level of productivity the couple experiences in their relationship. Productivity refers to the shared goals of the relationship that have been or are in the process of being realized as concrete areas of achievement that reflect back upon the couple.