I think I mentioned this - I was really down for a while after graduating college. I drowned in guilt and shame, grew numb, stopped caring, and eventually realized that since I was unwilling to consider offing myself, I might as well do something useful for someone else.
I decided that I'd try to please my parents, so I threw myself into job applications, got a part-time position, started making an effort because I had an obligation... and then I met a guy and we started dating and spent months in giddy infatuation... then I was promoted to full-time... then I got into a conflict with a pig-headed manager and worked my tail off to prove myself against her... she eventually got demoted... then I was promoted to assistant manager... then I moved into my own place... and recently I've decided my future career path, dropped to part-time, and gone back to school. I'm not back to 100% yet, but maybe 75%, maybe more. I've had a really good last two days and I'm getting there. Now I'm spending my energy on my relationship, my family, school, work, and trying to balance all of that. It's not always amazing of course but it feels meaningful because those are all things I really value. I feel like I'm back "in" the world instead of staring at it from outside.
Each time I stopped focusing as much on myself, it got easier. I don't mean this in terms of taking care of myself, but in terms of choosing an external goal and focusing on that. I feel like there's a really careful balance that has to be struck between taking care of yourself and prioritizing yourself, and getting sucked into the depressive world of nothing mattering but yourself. It's a really bizarre form of self-centeredness, one that simultaneously focuses on the self and puts down the self. And as a result, I think one potential antidote is to stop focusing on the self and to just go out in the world and do. To sort of, strangely, tell yourself that you're not going to listen to your negative judgments about yourself or your life for right now. Have you heard of vicious and virtuous cycles? The vicious depression cycle would be you judging that your life is meaningless, so you're more inclined to look for ways your life lacks meaning (thanks to confirmation bias), so you're more inclined to judge that your life is meaningless. Whereas the opposite virtuous cycle would be to judge that your life has meaning, so you're more inclined to look for ways your life has meaning, so you're more inclined to judge that your life has meaning. You just have to reverse the flow.
I didn't understand it then, but my parents told me that it was better to just go do something and not worry about whether it was an appealing thing or not. I remember this one day when I was still a part-timer and before I met my boyfriend when I was tying some bags or some really menial task and all of a sudden I realized that I was, completely inexplicably, content and joyful at that moment. I shouldn't have even liked the task if I wasn't depressey, but there the joy was. My dad's a psychiatrist and he's told me that they encourage people who are depressed to just keep doing the things they like, even if it doesn't seem enjoyable, because often what they find is that after doing it a number of times, the joy, inexplicably, starts to return. At least for me, I think a big part of it was getting out of my own head and not letting myself be so impacted by my negative opinion of my life.
I dunno, [MENTION=18694]Magic Qwan[/MENTION], if any of that's helpful, but that's been my personal experience with having felt numb and useless and that my life was meaningless, and having been lucky enough to have parents and peers who guided me back on a path of caring and color and feeling meaning in my life again. I know that it's possible and I hope you just keep trying!