the pdf link says 404
hey, sorry for not seeing this sooner. I don't go on itch much.
You can get "Feeling Good" the book I was talking about here:
https://archive.org/details/FeelingGood-TheNewMoodTherapy/mode/2up
I don't know what advice to give that can help another than the book really helped me and I would still recommend reading it.
It sucks to feel that way. Have you tried learning something or getting a new Hobby? Programming has helped me when I was down.