There are various marital therapeutic interventions that aim to enhance relationship satisfaction and the longevity of relationships. Researchers have found that level of commitment is more indicative of relationships longevity than relationship satisfaction. Therefore, couples who remain in unsatisfactory long-term relationships, perhaps are unsatisfied but they are highly committed to the relationship.
Relationship commitment hinges on dependency and size-of-investment. Dependency is how dependent partners are on one another. Is the partner able to have their needs met if they leave the relationship? Investment size is measured by gains and losses. How much the person has invested financially, physically, psychologically, and emotionally, and how much all these factors will decline if the person leaves the relationship. How much does the partner feel they invested in the relationship, and how much will they lose by leaving the relationship?
Relationship commitment is a cycle. The more one invests in their relationship, the more one becomes dependent on the relationship, the more one is dependent on the relationship, the more their losses go up, thereby equaling commitment. I am sure you are thinking, what is the point of commitment without relationship satisfaction!? The trick here is to achieve commitment plus satisfaction.
What research has also shown is that couples who have high commitment (dependency + investment size) take actions that are pro-relationship. They will choose behaviors that are beneficial for the relationship as a unit, rather than beneficial for only one partner. This creates what is called "mutual cyclic growth". The more one makes choices that are pro-relationship, the more the partners begin to trust one another, the more they trust, the more willing they are to become dependent on one another, the more dependent they are on one another, the more the investment size goes up, the more they act in pro-relationship ways. Bingo! Satisfaction + Commitment.
But, what’s if you are not yet at a sufficient commitment level to act in a pro-relationship? Harvey Hendriks in his Imago therapy and John Gottman in the Gottman Method, both found a way to target investment size and couple’s satisfaction at the same time - it is a win-win. In Gottman’s relationship exercise, "bids" and Hendricks exercise, "acts of kindness"; couples are encouraged to do acts of kindness and care for each other. Thereby, each partner has his/her needs met AND the investment size of the relationship continues to grow. When partners do acts of kindness, of affection, and of care they increase relationship satisfaction, thereby increasing investment size and again the mutual cyclic growth continues.