Why we become desperate?

why are we so intolerant of weakness today ? esp. when it comes to love or dating.. we usually dont want the person who likes us but the person who doesn't want us or like us. and this chain seems to be never ending and unforgiving. then as we realize that the one we love or want doesn't want us the same way but instead abhor's us.. we start to hold on it even more and tighter until finally we have completely destroyed our self esteem to the extent on purpose so that we might feel nothing and escape all the humiliation and heart break from the one we love.. or you would realize that living life without the one you love leaves no meaning in your life. Why are we so unforgiving and unwilling to understand another person's feelings in our lives ? why cant we respectfully break someone's heart without making them feel that they have absolutely nothing to offer.