The relationship is a mirror in which you can see yourself.
This mirror can either distort or expose the truth about yourself.
Most of us see in the relationship, in the mirror, what we preferably want to see, but we don´t see that, which is real. We like to condemn, justify, compare, or escape, and rather live in the past or the future, than to see the relations in which we are in the moment.
In this way the present, as Pascal said, only becomes used by the past as a passage to the future, and therefore the relationship – which is something that is in the moment, and not in past and future – becomes meaningless, wherefore there arises unreality and absence.