When 2 becomes One. Relationships are akin to a living flame- it thrives when two beomes one, and the passion igniting it is kept- warm and beating as a heart between two souls. Whether is it friendship, lovers or family or partners, the 'flames' within it keeps it alive and the stronger it burns, the closer they become.
Just like with all things, it requires both/all parties to give, to stoke the flames and kindle it, and when it becomes one sided, the heart cannot beat and thus the life dies with it, becomes cold and reflects the behavior or expression within the members. Dying flames can be rekindled, but dead cold hearts may never be revived without much effort and only if two are willing to do so.