Maybe it's easier to lead life thinking that people just don't care for you as much as you hoped/expected them to.
It reduces your reliance on them, and it's better than getting your hopes all crushed into tiny pieces.
And forget about changing other people. You know that even changing yourself doesn't come easy, so what makes you think that other people will change themselves? Especially when it's human nature to blame everything else but themselves - even when it's clearly that they're the ones in the wrong.
Also...other people have their own lives to lead. As if they'll bother with yours so much...
At the end of the day, it's just you against the world. You're the only one you can always count on to be there with you...whether or not you will act accordingly is still, after all, up to you.