Thanks To you and to the people who repped me about my post -- you guys really did make me feel a lot better.
I had been very unproductive that day when I needed to have been productive, and I was too tired (from it being late, and from several days in a row of not enough sleep) to think rationally, or get myself out of a downward thought spiral, let alone to start trying to make up for lost homework time.
BUT... now I am feeling chill ^_^ because I had a nice, relaxing evening of unstructured things that I can do on my own time, without forced scheduling -- and because I know that I will get enough sleep tonight, and it will be wonderful. I <3 weekends!
I'm happy. I think I have my heart back.
I spent the last night and this morning, with my eyes closed, listening to the sound of my breathing.
This time, when I said, "I don't want to do this anymore", I felt it. And I believed it.
Things will only be better after this.