Love's labour lost (?!)

"There is something incredibly ridiculous about the feelings of people who you've ceased to love, and, who have in turn ceased to love you."
--Oscar Wilde in 'The Picture of Dorian Gray'.

Why?

It almost feels like a mockery to try and understand, to sympathize with the ones you've "gotten over" (not necessarily the falling-in-love kind of love, it's the same with all the relationships where there was any kind of love involved, be it close friends, family, etc.), it all seems put on, seems fake, cheap and artificial.
What is lost from the bond? All that went into making it work in the first place, does it reduce to nothing? Or does one go into denial that they have not "gotten over" in the true sense of the word? What happens? Is it just that one's priorities change? Is it that there are other relations (in want of a better word here) that now demand the labouring over?
The same things that would've kept one awake through nights... trying to figure a solution for the loved-one, suddenly seems trivial to the point that one even forgets that their previously loved one needs them, and needs them desperately?!
Do all the times they've let you down, when you needed them and they conveniently overlooked your problems become a source of this indifference?
Now that it's all over, does this indifference make one a bad person? Does it make one heartless? Does it matter at all?

Why does my heart feel so heavy?!