For one, Happy Birthday.

Read through your reddit post, and you make sense to me.

I find myself less and less capable of doing something I enjoy, or doing something productive at all.

reading takes energy, and taking a walk across the city - the only option remotely appealing - is also beyond my reach right now.

If you'd like advice, then it's backtracking and continuing to pursue friendships or past friendships.

I've pushed away people in my life in the last few years, and now I have no one I can come to. I've been reaching out to people this year, but it doesn't seem to work

I want it to be special - and I want to spend it with people I care about, because it matters a lot to me.

The only thing harder than trying to get what you want is getting what you want. For me, if the first option is all the more scary, then my route was to seek out clubs and forcing myself to attend to meet people. I empathize with your perception of freshmen rejecting you as hurtful. I know that role as a mentor meant a lot to you on so many levels. If anything, a mentor will keep coming back to eventually become a friend. Their rejection turns into an opportunity for your relationship to grow onto equal footing. Finally,

It's always been a special day: a point in time when things could be about myself for once - something I can't allow to happen most of the time. People would come and smile to me and congratulate me, and it doesn't matter that the reason is superficial.

Assuming these people are your family, or even anyone in general, so long as they smile and congratulate you - whether it's superficial or not - isn't that all that matters? Even outside the context of it being your birthday? That's where relationships have room to grow, and sometimes where they start. For most of this year there's been a girl in my class I've been crushing on but haven't talked to until I forced myself to now that it's the end of the semester. With 2 weeks to go, I guarantee any form of communication that started (and occurred) between us was anything but superficial. It will build from there so long as you show interest in who they are and reciprocate any forthcoming gestures. Usually, initiating them repeatedly can set a good tone. Don't ask me about where we are now with that girl... but I hope the example for one was something. Also, in my experience, the best thing I can do for myself is taking a walk when I'm in a long funk. From your reddit post, it seems you and I both have considerable trouble getting out of our own headspace... as well as roomspace at times like these. Getting out at least brings a change of scenery as well as fresher air, if anything.