In the absence of an external force, a
relationship in motion tends to stay in motion. This is when a couple has been together for a long time, and even though they
don't seem overly happy with the situation, they stay in the
relationship because why not. They are comfortable and probably too scared to experience a dramatic change and take their chances alone or with someone else. When asked, they individually might say that they do not want to marry their current significant other, but they have no plans to end the
relationship and everyone pretty much assumes they will in fact get married even though their
relationship has lacked a spark for quite a while. Eventually the urge to experience what life outside of the stagnant relationship has to offer is overcome by the fear that now it might be too late or not worth it and so
people often succumb to RI, accepting lifelong mediocrity, perpetual what-ifs, and inevitable divorce down the road. RI usually causes more strife for all parties in the long run than it does if an individual acts proactively to avoid it and deals with the short term consequences. The longer RI exists, the more difficult it is to escape mentally, emotionally, and socially because of the awkwardness it would cause among family and friends if the relationship ended abruptly, as well as the overwhelming and growing guilt felt by the person who decides to end it.
Relationship inertia is sometimes seen when a couple gets into a serious
relationship at a young age, such as in high school, and then stays together for many years and/or through college even if they have outgrown each other, especially if one or both of the individuals' only sexual partner has been the other in which case
anxiety about sexual experience and an overly-stressed sense of loyalty also stabilize RI.
