to get clear idea of what is happening or has happened to relationship – we deal with psychology (not medicine or law, for example), so any change is possible. Get somebody fall in love, understand him or her, make up a quarrel, enliven, deepen, return, etc. No problem. There are tens of schools, hundreds of methods, thousands of techniques available.
But one pitfall can complicate it all. And this pitfall is a human desire for complexity to dwell. You are never as partly stuck in your partner as you are stuck in the state of stickness. No one is in love with somebody as strongly as he or she is in love with love itself. That is why objects of suffering can change several times through a decade though sufferings remain the same.