Why does a person get obsessive for those who don't take interest in him? Why does a person get obsessive, Specially towards those who don't accept his love or attraction towards them?

Self esteem has such an impact on human life that he wants to preserve his esteem in any way possible. Then why does one get obsessive towards those who have broken the trust he put into them? Why does he try to reason with those who have told him that they don't love him?

Where does his drive to consolidate his self esteem go in such situations?
Another component, which relies less on situations from one's past, are the effects of perceived scarcity. A paradigm in behavioral psychology which has become almost universally accepted is that the more scarce and hard to come by something is (be it a certain model of car, or the affection of another individual), the more valuable we perceive it to be. This is why a common sales tactic is to tell a potential customer that the item they are prospecting is one of the last in stock.

If you expand this principle into human interaction, its easy to understand why not reciprocating someone's interest can often lead them to double down and perhaps even desire attention and affection more than they originally had.