couples vacillate between commitment and ambivalence and often disagree on how committed they were as well as why they became committed in the first place.

event-driven

Explanation:

Event driven couples vacillate between commitment and ambivalence and often disagree on how committed they were as well as why they became committed in the first place. Event driven couples have relationships that are triggered based on recent happening in the couples lives with no orderliness in the progression of the relationship or commitment and such couples are unhappy as opposed to relationship driven couples which follow a pattern in the development of their relationship until they eventually get married and is more stable.