Objective... what, actually, do you want? I mean, what observable actions could people take that would convince you that they care?
EDIT: Also, what's your standard for "caring"?
I dunno.... maybe consistency?
There used to be people who were nice to me and I end up growing really attached to them, and when they leave me or just aren't there when I need them the most I find it very hard to trust them afterwards.
Well, that's a difficult one. Consistency is one of those things in life that's really nice, but hard to attain, simply because their own lives follow such different trajectories that they're just incapable of being there at the particular time you need them. It's one of those annoying things where you might deserve something, but there's no commensurate obligation on any particular other person to provide it. This is one of the most convincing reasons I've heard for marrying somebody, honestly; rooting your lives together so tightly gives you both a lot of the context needed to be able to understand the day-to-day stresses the other is under, and manage both your expectations and ability to give accordingly.
But, I'm digressing - it really does suck that people aren't consistently there for you when you need them. And they're bein' mighty unfair if they're just ditching you because it's inconvenient or something, especially if you've been making the effort to be there for them and you've communicated that you expect some reciprocity on the matter. I've gotta say, though, a forum is an absolute shit format for that; there are people around here I care about as deeply as anybody, and I still don't respond to every post they make. You'd be better served with chat or something, since I know your meatspace situation is basically drowning in a sea of assholes. And not in the good way.
Sorry if I come off as condescending, here. Happiness
is a matter of managing your expectations, but I find that it's more about examining how you define things and whittling down what you really want than it is about trying to convince yourself that what you have is really what you want. I mean, most of my happiest moments are when I'm furiously working toward something I don't, and often can't, have, for example.