Let's talk about how a person feels after a breakup. Between people, especially between people of different sexes, there is often a very strong attachment.
And when such people part, for any reason, it is very painful for them to perceive, since each of them identified his existence in union with another person.
I am not saying now that being alone is good or bad. It's just that initially a person is alone, and in relation to someone he satisfies any need. In this sense, there is no unconditional love, that is, love by default. Since love is determined by the satisfaction of needs in a relationship. In intersexual relations, for example, such needs are determined by the reproductive instinct.
Why does a person believe that love exists!
Moreover, it is absolutely not important who a person positions himself in such relations: as a follower or a leader, since the relationship, if they are voluntary, is always the satisfaction of personal needs. And that is why parting, in the first place, is the deprivation of the opportunity to satisfy one's own needs. In this sense, it is not connected with the loss of the opportunity to communicate with the person of any person as such, namely the loss of the opportunity to meet the reaction and react to what is familiar and what corresponds to his idea of a positive external stimulus.