In one respect man is the nearest thing to me, so far as I must do good to men and endure them. But so far as some men make themselves obstacles to my proper acts, man becomes to me one of the things which are indifferent, no less than the sun or wind or a wild beast. Now it is true that these may impede my action, but they are no impediments to my affects and disposition, which have the power of acting conditionally and changing: for the mind converts and changes every hindrance to its activity into an aid; and so that which is a hindrance is made a furtherance to an act; and that which is an obstacle on the road helps us on this road.
- Marcus Aurelius, Meditations, Book 5.20
Over the past few days, I've seen the minds of others turn to anguish and despair due to the actions of significant others. In their estimation, the action of the other - dumping them, hurting them, acting out against them - signifies an attack on their character, that they are no longer worthy of others' acceptance or love. On the contrary, their lovability and capacity to accept such love has not diminished in any way or form; they more or less are as they were prior to these events transpiring.
So why the inevitable turn to self-loathing and victimization when these relationships fail, even if it is of no to little fault of their own? Where is the rule that dictates this rigorous mental self-flagellation must occur? It may stem from a false-to-fact belief that their significant other is the only arbiter of romantic love and care for them and that this love must be given at all times otherwise the world is cruel, spiteful and out to get them.
In reality, save for the few who have only had one relationship prior (and have little experience of breaking up, conflict, etc.) the granting of love and care is ultimately a choice that is entered into mutually with varying degrees of intensity across both (or even multiple) parties. Rationally, if the choice is not beneficial to either or both parties, then another choice can be made as to repair or discontinue the relationship. It is also a choice to further the relationship by exchanging gifts, taking holidays together, moving in and marrying etc. This choice may be "obvious" and seen not even as a choice at all despite the perceived undesirable yet still viable alternatives (staying in one's own house, for example) that are available to either party.
Like any human with human rationality and agency, the choices we make are our own responsibility. It would be unfair to blame another for the choices that we make, even if they are reached by consensus in a romantic (or even platonic) relationship. Just because you were chosen by another as significant does not mean they afford you special dispensation when this significance is later withdrawn for whatever reason. One must always take care of himself within or without a relationship - how could one have functioned prior to the relationship forming with this belief? It was never and never will be the responsibility of someone else to take care of a rational, functional, adult human being. It would be rational to remember that your significant other was once an indifferent; it is not inconceivable to think that one day they may return to that role once again.